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Sculpture

Sculpture

A sculpture is a three-dimensional, man-made object selected for special recognition as art.

Materials of Sculpture

The materials of historical sculpture

The only historical sculptures that are available to us were those made with materials permanent enough to survive their environments until today. Sculpture made for royal courts or large public works were often produced in expensive durable materials, primarily bronze and stone such as marble, limestone, porphyry, and granite. More rarely precious materials such as gold and ivory were used for chryselephantine works. More common and less expensive materials were used for sculpture for wider consumption, including wood such as oak, box and lime; terracotta and other ceramics; spelter; and metals such as pewter. Although rarely used for final works, the sculptor would make use of ephemeral materials such as plaster of paris, wax, clay and even plasticine in the case of the victorian Alfred Gilberts maquettes for 'Eros' at Piccadilly Circus, London.

Contemporary materials

maquette, England. This was sculpted with a chain saw from a standing tree, which was diseased and due to be felled]] Most traditional sculpture materials are still in wide use today. However, advancements in technology and changes have broadened the range of materials sculptors can choose to use, including glass and sand, aluminum, polymers and many other synthetic materials, and liquid crystals. Some sculptures are multimedia, for example sound sculptures which, as their name implies, produce sound. Many artists use video and computers in their sculptures as well. Computers and motors can also be used in sculptures, leading to works that may be classified as robotic. Sculptors are constantly searching for new ways to make art and for new materials to make it with, including blood, feces, dead animals. See also body fluids in art. Andy Goldsworthy is notable at a sculptor for his use of almost entirely natural materials in natural settings. In his late writings, Joan Miró even proposed that some day sculptures might be made of gases; see gas sculpture.

Sculpture around the world

:See also History of sculpture

Asian

:See also Buddhist art Many different forms of sculpture were in use in the many different regions of Asia, often based around the religions of Hinduism and Buddhism. A great deal of Cambodian Buddhist sculpture is preserved at Angkor, however organized looting has had a heavy impact on many sites around the country. Also see Angkor Wat. In Thailand, sculpture was almost exclusively of Buddha images. Many Thai sculptures or temples tended to be gilded, and on occasion enriched with inlays. See also Thai art

India

:See also Indian Art During the 2nd to 1st century BCE in India, sculptures became more explicit, representing episodes of the Buddha’s life and teachings. Although India had a long sculptural tradition and a mastery of rich iconography, the Buddha was never represented in human form, but only through some of his symbols. Gandharan Buddhist sculpture displays Greek artistic influence, and it has been suggested that the concept of the “man-god” was essentially inspired by Greek mythological culture. Artistically, the Gandharan school of sculpture is said to have contributed wavy hair, drapery covering both shoulders, shoes and sandals, acanthus leaf decorations, etc. The pink sandstone sculptures of Mathura evolved during the Gupta period (4th to 6th century) to reach a very high fineness of execution and delicacy in the modeling. Sculptures in Afghanistan, in stucco, schist or clay, display very strong blending of Indian post-Gupta mannerism and Classical influence, Hellenistic or possibly even Greco-Roman.

China

:See also Chinese art Chinese artifacts date back as early as 10,000 BC -- and skilled,Chinese artisans have been active up to the present time -- but the bulk of what is displayed as sculpture in Euro-culture museums come from a few, select, historical periods. The first period of interest has been the Zhou dynasty (1050-771 BC), from which come a variety of intricate bronze vessels. The next period of interest was the Han Dyanasy ( 206 BC - 220 AD) -- beginning with the spectacular Terracotta army assembled for the tomb of the first emperor of the very brief Chin dynasty that preceded it. (Qin Shi Huang) in 210–209 BC.) Tombs excavated from the Han period have revealed many figures found to be vigorous, direct, and appealing 2000 years later. The period now considered to be China's golden age is the Tang Dynasty. (coinciding with what in Europe is sometimes called "The Dark Ages". Decorative figures like those shown below became very popular in 20th Century Euro-American culture, and were made available in bulk as warlords in the Chinese civil wars exported them to raise cash: Considered especially desirable, and even profound, was the Buddhist sculpture, often monumental, begun in the Sui Dynasty, inspired by the Indian art of the Gupta period, and many are considered treasures of world art: Following the Tang, Western interest in Chinese artifacts drops off dramatically, except for might be considered ornamental furnishings, and especially objects in jade. Pottery from many periods have been collected, and again the Tang period stands out apart for its free, easy feeling. Chinese sculpture has no nudes --other perhaps than figures made for medical training or practice -- and very little portraiture compared with the European tradition. One place where sculptural portraiture was pursued, however, was in the monasteries: Almost nothing, other than jewelry, jade, or pottery is collected by art museums after the Ming period ended in the late 17th century -- and absolutely nothing has yet been recognized as sculpture from the tumultuous 20th century, although there was a school of Soviet-influenced social realist sculpture in the early decades of the Communist regime, and as the century turned, Chinese craftsmen began to dominate commerical sculpture genres (the collector plates, figurines, toys, etc) and avant garde Chinese artists began to participate in the Euro-American enterprise of contemporary art. Image:AIC-winejar2.jpg Image:XianCavalryman.JPG Image:AIC-chimera.jpg Image:AIC-hantomb.jpg Image:AIC-tang-rider2.jpg Image:AIC-tang-girl.jpg Image:AIC-Boddhisatva-side.jpg Image:AIC-jade-dragon-cup.jpg Image:AIC-lushanjar.jpg Image:AIC-portrait-monk.jpg Image:Doctors lady.jpg

Japan

:See also Japanese art, Japanese sculpture Countless paints and sculpture were made, often under governmental sponsorship. Most Japanese sculpture is associated with religion, and the medium's use declined with the lessening importance of traditional Buddhism. During the Kofun period of the third century, clay sculptures called haniwa were erected outside tombs. Inside the Kondo at Horyu-ji is a Shaka Trinity (623), the historical Buddha flanked by two bodhisattvas and also the Guardian Kings of the Four Directions The wooden image ( 9th c.) of Shakyamuni, the "historic" Buddha, enshrined in a secondary building at the Muro-ji, is typical of the early Heian sculpture, with its ponderous body, covered by thick drapery folds carved in the hompa-shiki (rolling-wave) style, and its austere, withdrawn facial expression. The Kei school of sculptors, particularly Unkei, created a new, more realistic style of sculpture. The two Nio guardian images (1203) in the Great South Gate of the Todaiji in Nara illustrate Unkei's dynamic suprarealistic style.

Africa

:See also African art African art has an emphasis on Sculpture - African artists tend to favor three-dimensional artworks over two-dimensional works. The earliest known sculptures are from the Nok culture of Nigeria, made around 500 BCE.

Egypt

:See also Art of Ancient Egypt The ancient art of Egyptian sculpture evolved to represent the ancient Egyptian gods, and Pharaohs, the divine kings and queens, in physical form. Very strict conventions were followed while crafting statues: male statues were darker than the female ones; in seated statues, hands were required to be placed on knees and specific rules governed appearance of every Egyptian god. Artistic works were ranked according to exact compliance with all the conventions, and the conventions were followed so strictly that over three thousand years, very little changed in the appearance of statutes.

United States

The history of sculpture in the United States reflects the country's 18th century foundation in Roman republican civic values as well as Protestant Christianity. American sculpture of the mid to late 19th century was often classical, often romantic, but showed a special bent for a dramatic, narrative, almost journalistic realism. Public buildings of the first half of the 20th century often provided an architectural setting for sculpture, especially in relief. In the 1950s traditional sculpture education would almost be completely replaced by a Bauhaus influenced concern for abstract design. Minimalist sculpture (Richard Serra) often replaced the figure in public settings. Modern sculptors use both classical and abstract inspired designs.

Europe

An overview of forms abstract bust at the Victoria and Albert Museum, 19th century.]] Some common forms of sculpture are:
- The bust, a representation of a person from the chest up.
- Equestrian (horse) sculpture
- Free-standing sculpture, not intended to be displayed on a pedestal or shelf
- Fountain
- "In the round": designed by the sculptor to be viewed from any angle.
- Jewellery
- Mobile (See also Calder's Stabiles.)
- Relief: sculpture still attached to a background, standing out from that ground in "High Relief" or "Low Relief" (bas relief)
- Site-Specific Art
- Statue Statue] Perhaps the majority of public art is sculpture. See also sculpture garden.

Greek-Roman-classical

:See also Sculpture of Ancient Greece Features unique to the European Classical tradition: #full figures: using the young, athletic male or full-bodied female nude #portraits: showing signs of age and strong character #use of classical costume and attributes of classical deities #Concern for naturalism based on observation, often from live models. Features that the European Classical tradition shares with many others: #characters present an attitude of distance and inner contentment #details do not disrupt a sense of rhythm between solid volumes and the spaces that surround them #pieces feel solid and larger than they really are #ambient space feels sacred or timeless The topic of Nudity Sculpture of Ancient Greece A Nude or 'unadorned' figure in Greek classical sculpture was a reference to the status or role of the depicted person, deity or other being. Athletes, priestesses and gods could be identified by their adornment or lack of it. The Renaissance preoccupation with Greek classical imagery, such as the 4th century B.C. Doryphoros of Polykleitos, led to nude figurative statues being seen as the 'perfect form' of representation for the human body. Subsequently, nudity in sculpture and painting has represented a form of ideal, be it innocence, openness or purity. Nude sculptures are still common. As in painting, they are often made as exercises in efforts to understand the anatomical structure of the human body and develop skills that will provide a foundation for making clothed figurative work. Nude statues are usually widely accepted by most societies, largely due to the length of tradition that supports this form. Occasionally, the nude form draws objections, often by fundamentalist moral or religious groups. Classic examples of this are the removal of penises from the Vatican collection of Greek sculpture and the addition of a fig leaf to a plaster cast of Michelangelo's sculpture of David for Queen Victoria's visit to the British Museum. The topic of social status Worldwide, sculptors are usually tradesmen whose work is unsigned. But in the Classical tradition, some sculptors began to receive individual recognition in Periclean Athens and more so in the Renaissance revival 2000 years later, culminating in the career of Michelangelo who entered the circle of princes. Sculpture was still a trade, but exceptional sculptors were recognized on a level with exceptional poets and painters. In the 19th century, sculpture also became a bourgeois/upper class avocation, as poetry and painting had been, and the classical work of women sculptors began to appear.

Gothic

Gothic sculpture evolved from the early stiff and elongated style, still partly Romanesque, into a spatial and naturalistic feel in the late 12th and early 13th century. The architectural statues at the Western (Royal) Portal at Chartres Cathedral (ca. 1145) are the earliest Gothic sculptures and were a revolution in style and the model for a generation of sculptors. Prior to this there had been no sculpture tradition in Ile-de-France—so sculptors were brought in from Burgundy. The Bamberg Cathedral had the largest assemblage of 13th century sculpture. In England sculpture was more confined to tombs and non-figurine decorations. In Italy there was still a Classical influence, but Gothic made inroads in the sculptures of pulpits such as the Pisa Baptistery pulpit (1269) and the Siena pulpit. Dutch-Burgundian sculptor Claus Sluter and the taste for naturalism signaled the beginning of the end of Gothic sculpture, evolving into the classicistic Renaissance style by the end of the 15th century.

Renaissance

:See also Renaissance Renaissance Renaissance ]] Sculpture was also revived, in many cases before the other arts. There was a very obvious naturalism about contemporary sculpture, and highly true to life figures were being sculpted. One of the most important sculptors in the classical revival was Donatello. His greatest achievement of his classic period is the bronze David (not to be confused with Michelangelo's David), which is currently located at the Bargello in Florence. At the time of its creation, it was the first free-standing nude statue since ancient times. Conceived fully in the round and independent of any architectural surroundings, it was the first major work of Renaissance sculpture. Among the many sculptures of Michelangelo are those of David and the Pietà, as well as the Doni Virgin, Bacchus, Moses, Rachel, Leah, and members of the Medici family. Michelangelo's David is possibly the most famous sculpture in the world, which was unveiled on September 8, 1504. It is an example of the contrapposto style of posing the human figure. Michelangelo's statue of David differs from previous representations of the subject in that David is depicted before his battle with Goliath and not after the giant's defeat. Instead of being shown victorious over a foe much larger than he, David looks tense and ready for combat.

Mannerist

Benvenuto Cellini created a salt cellar of gold and ebony in 1540 featuring Neptune and Amphitrite (earth and water) in elongated form and uncomfortable positions. It is considered a masterpiece of Mannerist sculpture.

Baroque

contrapposto]] In Baroque sculpture, groups of figures assumed new importance, and there was a dynamic movement and energy of human forms— they spiralled around an empty central vortex, or reached outwards into the surrounding space. For the first time, Baroque sculpture often had multiple ideal viewing angles. The characteristic Baroque sculpture added extra-sculptural elements, for example, concealed lighting, or water fountains. Bernini was undoubtedly the most important sculptor of the Baroque period. His first works were inspired by Hellenistic sculpture of ancient Greece and imperial Rome he could study in the new seat. One of his most famous works is Ecstasy of St Theresa

Neo-Classical

The sculpture examples they actually embraced were more likely to be Roman copies of Hellenistic sculptures. In sculpture, the most familiar representatives are the Italian Antonio Canova, the Englishman John Flaxman and the Dane Bertel Thorvaldsen.

Modernism

Modern Classicism contrasted in many ways with the classical sculpture of the 19th Century which was was characterized by commitments to naturalism (Antoine-Louis Barye) -- the melodramatic (François Rude) sentimentality (Jean Baptiste Carpeaux)-- or a kind of stately grandiosity (Lord Leighton) Several different directions in the classical tradition were taken as the century turned, but the study of the live model and the post-Renaissance tradition was still fundamental to them. Lord Leighton, France.]] Auguste Rodin was the most renowned European sculptor of the early 20th century. He might be considered as sui generis -- that is, if anyone successfully composed in his turbulent, virtuosic style, they have yet to be discovered. But he is often considered a sculptural Impressionist, like Medardo Rosso, Count Troubetski, and Rik Wouters, attempting to frame the charm of a fleeting moment of daily life. Modern Classicism showed a lesser interest in naturalism and a greater interest in formal stylization. Greater attention was paid to the rhythms of volumes and spaces - as well as greater attention to the contrasting qualities of surface (open, closed, planar, broken etc) while less attention was paid to story-telling and convincing details of anatomy or costume. Greater attention was given to psychological realism than to physical realism. Greater attention was given to showing what was eternal and public, rather than what was momentary and private. Greater attention was given to examples of ancient and Medieval sacred arts:Egyptian, Middle Eastern, Asian, African, and Meso-American. Grandiosity was still a concern, but in a broader, more world-wide context. Early masters of modern classicism included: Aristide Maillol,Alexander Matveev, Joseph Bernard, Antoine Bourdelle, Georg Kolbe, Libero Andreotti, Gustav Vigeland, Jan Stursa As the century progressed, modern classicism was adopted as the national style of the two great European totalitarian empires: Nazi Germany and Soviet Russia, who co-opted the work of early masters, like Kolbe and Arno Breker in Germany, and Matveev in Russia. Nazi Germany had a 15-year run; but over the 70 years of the USSR, new generations of sculptors were trained and chosen within their system, and a distinct style, socialist realism, developed, that returned to the 19th century's emphasis on melodrama and naturalism. socialist realism In the rest of Europe, the modern classical became either more decorative/art deco (Paul Manship,Carl Milles) or more abstractly stylized (Henry Moore, Alberto Giacometti,Julio González (sculptor)) or more expressive (and Gothic) (Anton Hanak,Wilhelm Lehmbruck, Ernst Barlach, Arturo Martini) -- or turned more to the Renaissance (Giacomo Manzu, Venanzo Crocetti) or stayed the same (Charles Despiau, Marcel Gimond). Classical training was rooted out of art education in Western Europe (and the Americas) by 1970 and the classical variants of the 20th Century were marginalized in the history of modernism. But classicism continued as the foundation of art education in the Soviet academies until 1990, providing a foundation for expressive figurative art throughout eastern Europe and parts of the Middle East. By the year 2000, the European classical tradition maintains a wide appeal to viewers -especially tourists - and especially for the ancient, Renaissance, Baroque, and 19th century periods -- but awaits an educational tradition to revive its contemporary development. Modernist movements included Cubism, Futurism, Minimalism, Installation art and Pop-Art.

Contemporary Sculpture genres

Some modern sculpture forms are now practiced outdoors, and often in full view of spectators, thus giving them kinship to performance art in the eyes of some. Ice sculpture is a form of sculpture that uses ice as the raw material. Popular in China, Japan, Canada, Sweden and Russia. Ice sculptures feature decoratively in some cuisines, especially in Asia. Kinetic sculptures are sculptures that are designed to move, which include Mobiles. Snow sculptures are usually carved out of a single block of snow about 6 to 15 feet on each side and weighing about 20 - 30 tons. The snow is densely packed into a form after having been produced by artificial means or collected from the ground after a snowfall. Sound sculptures take the form of indoor sound installations, outdoor installations such as aeolian harps, automatons, or be more or less near conventional musical instruments. Sound sculpture is often site-specific. A Sand castle can be regarded as a sand sculpture. Other arts which can be regarded as sculptures include:
- Hologram
- pottery
- glass blowing
- costume
- mask
- doll

Greenfield Products Pty Ltd v. Rover-Scott Bonnar Ltd

The Australian copyright case of Greenfield Products Pty Ltd v. Rover-Scott Bonnar Ltd (1990) 17 IPR 417 is authority for the proposition that a thing not intended to be a sculpture is not a sculpture. This seems contrary to some famous examples of sculpture, including Marcel Duchamp's 1917 sculpture consisting of a porcelain urinal lying on its back, titled Fountain, and Carl Andre's sculpture Equivalent III exhibited in the Tate Gallery in 1978, consisting of bricks stacked in a rectangle.

External links

Sculpture basic topics, Portugal]]
- [http://engcom.ipsec.ro/Brancusi/index.html Sculptors from Romania] - Sculptors from Romania
- [http://www.modernsculpture.com/ ModernArts & ModernSculpture.com] - shows contemporary and some historical sculpture
- [http://www.sculptor.org www.sculptor.org, sculptor.org] - resources for sculptors
- [http://www.sculpture.org International Sculpture Center]
- [http://www.sculpture.org.uk/ Cass Sculpture Foundation]
- [http://www.traces.ws/sculpture Traces] - career resource for stone sculptors
- [http://www.scultura-italiana.com/ The Italian Sculpture!] - many images of historical sculptures
- [http://aboutstone.org/ About Stone] - About Stone fosters mutual interests, understanding and contacts amongst people who work with stone Sculpture Category:Arts ja:彫刻 simple:Sculpting

Three-dimensional

Three dimensional, 3-D or 3D may refer various topics, including:
- Stereoscopy, recording 3 dimensional visual information or creating the illusion of depth in an image
- Stereogram, a 3-D image illusion
- 3D computer graphics
- 3-D film, 3-D movie history
- Robert Del Naja, the stage name of the UK artist and musician
- 3D/Biela,in astronomy, Biela's Comet
- List of professional wrestling finishing maneuvers, a finishing maneuver in professional wrestling
- Ring binder, where a "3-D binder" has three D rings simple:3-D

Bronze

Bronze is the ancient name for a broad range of alloys of copper, but usually with tin as the main additive. First used in the Bronze Age, it made tools, weapons and armor harder or more durable than their stone and copper predecessors. In early use, the impurity arsenic made the alloy even harder. The earliest bronzes date to the late 4th millennium BC in Susa (Iran) and some ancient sites in Luristan (Iran) and Mesopotamia (Iraq). Bronze was stronger than the era's iron; quality steels were not available until thousands of years later. But the Bronze Age gave way to the Iron Age, perhaps because the shipping of tin around the Mediterranean became more limited during the major population migrations around 1200 – 1100 BC, which dramatically limited supplies and raised prices.[http://www.claytoncramer.com/Iron2.pdf] Bronze was still used during the Iron Age, but for many purposes the weaker iron was sufficiently strong. As ironworking improved, iron became both cheaper and stronger, eclipsing bronze in Europe by the early to mid-Middle Ages. Copper-based alloys have lower melting points than steel and are more readily produced from their constituent metals. They are generally about 10 percent heavier than steel, although alloys using aluminium or silicon may be slightly less dense. Bronzes are softer and weaker than steel, and more elastic, though bronze springs are less stiff (lower energy) for the same bulk. Bronzes resist corrosion (especially seawater corrosion) and metal fatigue better than steel. Bronzes also conduct heat and electricity better than most steels. The cost of copper-base alloys is generally higher than that of steels but lower than that of nickel-base alloys. Copper and its alloys have a huge variety of uses that reflect their versatile physical, mechanical, and chemical properties. Some common examples are the high electrical conductivity of pure copper, the excellent deep-drawing qualities of cartridge case brass, the low-friction properties of bearing bronze, the resonant qualities of bell bronze, and the resistance to corrosion by sea water by several bronze alloys. In the twentieth century, silicon was introduced as the primary alloying element, creating an alloy with wide application in industry and the major form used in contemporary statuary. Aluminium is also used for the structural metal Aluminium bronze. Bronze is the most popular metal for top-quality bells and cymbals, and also for cast metal sculpture (see bronze sculpture). Common bronze alloys often have the unusual and very desirable property of expanding slightly just before they set, thus filling in the finest details of a mould. Bronze also has very little metal-on-metal friction, which made it invaluable for the building of cannon where iron cannonballs would otherwise stick in the barrel. Bronze is still widely used today for springs, bearings, bushings and similar roles, and is particularly common in the bearings on small electric motors. Phosphor bronze is particularly suited to precision-grade bearings and springs. Bronze is typically 60% copper and 40% tin. Alpha bronze consists of the alpha solid solution of tin in copper. Alpha bronze alloys of 4-5% tin are used to make coins, springs, turbines and blades.

External links

- [http://www.jepsculpture.com/bronze.html Flash animation of lost-wax casting]
- [http://www.modernsculpture.com/bronze.htm Bronze Casting process explained - good pictures] Category:Copper alloys Category:Art materials ko:청동 ja:青銅

Limestone

, Tennessee]] Limestone is a chemical sedimentary rock composed largely of the mineral calcite (calcium carbonate: CaCO₃). Limestones often contain variable amounts of silica in the form of chert or flint, as well as amounts of clay, silt and sand as disseminations, nodules, or layers within the rock unit. The primary source of this calcite is most commonly marine organisms. These organisms secrete shells that settle out of the water column and are deposited on ocean floors as pelagic ooze (see lysocline for information on calcite dissolution). Secondary calcite may also be deposited by supersaturated meteoric waters (groundwater that precipitates the material in caves). This produces speleothems such as stalagmites and stalactites. Another form is composed of oolites (oolitic limestone) and can be recognised by its granular appearance. Limestone makes up about 10 percent of the total volume of all sedimentary rocks. oolites Pure limestones are white or almost white. Because of impurities, such as clay, sand, organic remains, iron oxide and other materials, many limestones exhibit different colors, especially on weathered surfaces. Limestone may be crystalline, clastic, granular, or massive, depending on the method of formation. Crystals of calcite, quartz, dolomite or barite may line small cavities in the rock. Travertine is a banded, compact variety of limestone formed along streams, particularly where there are waterfalls and around hot or cold springs. Calcium carbonate is deposited where evaporation of the water leaves a solution that is supersaturated with chemical constituents of calcite. Tufa, a porous or cellular variety of travertine, is found near waterfalls. Coquina is a poorly consolidated limestone composed of pieces of coral or shells. During regional metamorphism limestone recrystallizes into marble. Limestone is a parent material of Mollisol soil group.

Limestone landscape

Limestone is partially soluble, especially in acid, and therefore forms many erosion landforms. These include limestone pavements, pot holes, caves and gorges. Such erosion landscapes are known as karsts. Limestone is less resistant than most igneous rocks, but more resistant than most other sedimentary rocks. Limestone is therefore usually associated with hills and downland and occurs in regions with other sedimentary rocks, typically clays. clay Bands of limestone emerge from the Earth's surface in often spectacular rocky outcrops and islands. Examples include the Burren in Co. Clare, Ireland; the Verdon Gorge in France; Malham Cove in North Yorkshire, England; and the Ha Long Bay National Park in [[Vietnam{commonscat|Limestone

Granite

Granite is a common and widely-occurring group of intrusive felsic igneous rocks that form at great depths and pressures under continents. Granite consists of orthoclase and plagioclase feldspars, quartz, hornblende, biotite, muscovite and minor accessory minerals such as magnetite, garnet, zircon and apatite. Rarely, a pyroxene is present. Ordinary granite always carries a small amount of plagioclase, but when this is absent the rock is referred to as alkali granite. An interesting proportion of plagioclase feldspar causes granite to pass into granodiorite. A rock consisting of equal proportions of orthoclase and plagioclase plus quartz may be considered a quartz monzonite. A granite containing both muscovite and biotite micas is called a binary granite. Depending upon the proportions of feldspar and quartz, the Mohs hardness of granite ranges between 5.5 and 7 [http://www.findstone.com/daniel1.htm]. The average density is 2.75 g/cm<sup>3</sup> with a range of 1.74 to 2.80. The extrusive equivalent of plutonic granite rock is called Rhyolite. The word granite comes from the Latin granum, a grain, in reference to the coarse-grained structure of such a crystalline rock.

Occurrence

Granite occurs as relatively small, less than 100 km<sup>2</sup> stock-like masses and as large batholiths often associated with orogenic mountain ranges and is frequently of great extent. Small dikes of granitic composition called aplites are associated with granite margins. In some locations very coarse-grained pegmatite masses occur with granite. Granite has been intruded into the crust of the Earth during all geologic periods; much of it is of Precambrian age. Granite is widely distributed throughout the continental crust of the Earth and is the most abundant basement rock that underlies the relatively thin sedimentary rock veneer of the continents.

Origin

There are two theories for the origin of granite. The magmatic theory states that granite is derived by the crystal fractionation of magma. Thus granite bodies are the result of intrusion of liquid magma into the existing rocks. The granitization theory states that granite is formed in place by extreme metamorphism. There is evidence to support both theories, and both are useful to explain different observed features. The two may actually merge: as metamorphic conditions increase to the melting point of the metamorphosed granite, it will melt and become a liquid magma, and then harden into igneous granite.

Uses

Antiquity

The Red Pyramid of Ancient Egypt (c.26th century BC), named for the light crimson hue of its exposed granite surfaces, is the third largest of Egyptian pyramids. Menkaure's Pyramid, likely dating to the same era, was constructed of limestone and granite blocks. The Great Pyramid of Giza (c.2580 BC) contains a huge granite sarcophagus fashioned of "Red Aswan Granite." The mostly ruined Black Pyramid dating from the reign of Amenemhat III once had a polished granite pyramidion or capstone, now on display in the main hall of the Egyptian Museum in Cairo (see Dahshur). Other uses in Ancient Egypt, [http://www.eeescience.utoledo.edu/Faculty/Harrell/Egypt/Mosques/CAIRO_Rocks_1.htm] include columns, door lintels, sills, jambs, and wall and floor veneer. How the Egyptians worked the solid granite is still a matter of debate. Dr. Patrick Hunt [http://hebsed.home.comcast.net/hunt.htm] has postulated that the Egyptians used emery shown to have higher hardness on the Mohs scale.

Modern

Granite has been extensively used as a dimension stone and as flooring tiles in public and commercial buildings and monuments. Polished granite has been a popular choice for kitchen countertops due to its high durability and aesthetic qualities. In the world of sports, curling rocks are traditionally fashioned of granite. <center> <gallery> Image:Granite azul noce.jpg|<center>Azul Noce (Spain)</center> Image:Granite giallo.jpg|<center>Giallo Veneziano (Brazil)</center> Image:Granite_gran_violet.jpg|<center>Gran Violet (Brazil)</center> Image:Granite lavanda blue.jpg|<center>Lavanda Blue (Brazil)</center> </gallery> </center>

External link

- [http://www.geologynet.com/granite1.htm The Emplacement and Origin of Granite] Category:Igneous rocks Category:Granite domes ko:화강암 ja:花崗岩

Gold

Gold is a chemical element in the periodic table that has the symbol Au (L. aurum) and atomic number 79. A soft, shiny, yellow, dense, malleable, ductile (trivalent and univalent) transition metal, gold does not react with most chemicals but is attacked by chlorine, fluorine and aqua regia. The metal occurs as nuggets or grains in rocks and in alluvial deposits and is one of the coinage metals. For millennia, gold has served as money and is also used in jewelry, dentistry, and in electronics. Gold forms the basis for a monetary standard used by the International Monetary Fund (IMF) and the Bank for International Settlements (BIS). Its ISO currency code is XAU.

Notable characteristics

Gold is a metallic element with a characteristic yellow color, but can also be black or ruby when finely divided, while colloidal solutions are intensely colored and often purple. These colors are the result of gold's plasmon frequency lying in the visible range (due to a relativistic effect), which causes red and yellow light to be reflected, and blue light to be absorbed. It is one of only three metals which have an actual easily-identifiable color; the other two are copper, which is red, and caesium, which has a pale golden color. It is the most malleable and ductile metal known; a single gram can be beaten into a sheet of one square meter, or an ounce into 300 square feet. A soft metal, gold will readily form alloys with many other metals. This can be done to increase its strength, or create several exotic colors, sold for instance in the western United States to the tourist trade as "Black Hills" gold. Adding copper yields a redder metal, iron blue, Silver produces green, aluminium purple, platinum metals white, and natural bismuth together with silver alloys produce black. Native gold contains usually eight to ten per cent silver, but often much more — alloys with a silver content over 20% are called electrum. As the amount of silver increases, the color becomes whiter and the specific gravity lower. Gold is a good conductor of heat and electricity, and is not affected by air and most reagents. Heat, moisture, oxygen, and most corrosive agents have very little chemical effect on gold, making it well-suited for use in coins and jewelry; conversely, halogens will chemically alter gold, and aqua regia dissolves it. Common oxidation states of gold include +1 (gold(I) or aurous compounds) and +3 (gold(III) or auric compounds). Gold ions in solution are readily reduced and precipitated out as gold metal by the addition of virtually any other metal as the reducing agent. The added metal is oxidized and dissolves allowing the gold to be displaced from solution and be recovered as a solid precipitate. Recent research undertaken by Frank Reith of the Australian National University shows that microbes play an important role in the formation of gold deposits, transporting and precipitating gold to form grains and nuggets that collect in alluvial deposits. [http://www.abc.net.au/science/news/enviro/EnviroRepublish_1032376.htm]

Applications

Pure gold is too soft for ordinary use and is hardened by alloying with silver, copper, and other metals. Gold and its many alloys are most often used in jewelry, coinage and as a standard for monetary exchange in many countries. Because of its high electrical conductivity and resistance to corrosion and other desirable combinations of physical and chemical properties, gold also emerged in the late 20th century as an essential industrial metal.
- Gold can be made into thread and used in embroidery.
- Gold performs critical functions in computers, communications equipment, spacecraft, jet aircraft engines, and a host of other products.
- The resistance to oxidation of gold has led to its widespread use as thin layers electroplated on the surface of electrical connectors to ensure a good connection.
- Gold is used in restorative dentistry especially in tooth restorations such as crowns and bridges.
- Colloidal gold (a gold nanoparticle) is an intensely colored solution that is currently studied in many labs for medical, biological and other applications. It is also the form used as gold paint on ceramics prior to firing.
- Chlorauric acid is used in photography for toning the silver image.
- Gold(III) chloride is used as a catalyst in organic chemistry. It is also the usual starting point for making other gold compounds.
- Disodium aurothiomalate is a treatment for rheumatoid arthritis (administered intramuscularly). It inhibits lymphocyte proliferation, lysosomal enzyme release, the release of reactive oxygen species from macrophages, and IL-1 production. However, it can also cause photosensitive rashes, gastrointestinal disturbance, and kidney damage.
- The gold isotope Au-198, (half-life: 2.7 days) is used in some cancer treatments and for treating other diseases.
- Gold is used as a coating enabling biological material to be viewed under a scanning electron microscope.
- Many competitions and honors, such as the Olympics and the Nobel Prize, award a gold medal to the winner (with silver to the second-place finisher, and bronze to the third.)
- Since it is a good reflector of both infrared and visible light, it is used for the protective coatings on many artificial satellites.
- Gold flake is used on and in some gourmet sweets and drinks. Having no reactivity it adds no taste but is taken as a delicacy.
- White gold (an alloy of gold with platinum, palladium, nickel, and/or zinc) serves as a substitute for platinum.
- Green gold (a gold/silver alloy) is used in specialized jewelry while gold alloys with copper (reddish color) are more widely used for that purpose (rose gold).

History

rose gold Gold (Sanskrit jval, Greek χρυσος [khrusos], Latin aurum for "shining dawn", Anglo-Saxon gold, Chinese 金 [jīn]) has been known and highly valued since prehistoric times. It may have been the first metal used by humans and was valued for ornamentation and rituals. Egyptian hieroglyphs from as early as 2600 BC describe gold, which king Tushratta of the Mitanni claimed was as "common as dust" in Egypt. Egypt and Nubia had the resources to make them major gold-producing areas for much of history. Gold is also mentioned several times in the Old Testament. The south-east corner of the Black Sea was famed for its gold. Exploitation is said to date from the time of Midas, and this gold was important in the establishment of what is probably the world's earliest coinage in Lydia between 643 and 630 BC. The European exploration of the Americas was fueled in no small part by reports of the gold ornaments displayed in great profusion by Native American peoples, especially in Central America, Peru, and Colombia. Gold has long been considered one of the most precious metals, and its value has been used as the standard for many currencies (known as the gold standard) in history. Gold has been used as a symbol for purity, value, royalty, and particularly roles that combine these properties (see gold album). Gold in antiquity was relatively easy to obtain geologically; however, 75% of all gold ever produced has been extracted since 1910.[http://www.goldsheetlinks.com/production2.htm] It has been estimated that all the gold in the world that has ever been refined would form a single cube 20 m (66 ft) a side. The primary goal of the alchemists was to produce gold from other substances, such as lead — presumably by the interaction with a mythical substance called the philosopher's stone. Although they never succeeded in this attempt, the alchemists promoted an interest in what can be done with substances, and this laid a foundation for today's chemistry. Their symbol for gold was the circle with a point at its center (☉), which was also the astrological symbol, the Egyptian hieroglyph and the ancient Chinese character for the Sun (now 日). For modern attempts to produce artificial gold, see gold synthesis. During the 19th century gold rushes occurred whenever large gold deposits were discovered, including the California, Colorado, Otago, Australia, Witwatersrand, Black Hills, and Klondike gold rushes. Because of its historically high value, much of the gold mined throughout history is still in circulation in one form or another.

Value

Klondike] Klondike Like other precious metals, gold is measured by troy weight and by grams. When it is alloyed with other metals the term carat or karat is used to indicate the amount of gold present, with 24 carats being pure gold and lower ratings proportionally less. The purity of a gold bar can also be expressed as a decimal figure ranging from 0 to 1, known as the millesimal fineness, such as 0.995. The price of gold is determined on the open market, but a procedure known as the Gold Fixing in London, originating in 1919, provides a twice-daily benchmark figure to the industry. Historically gold was used to back currency in an economic system known as the gold standard in which one unit of currency was equivalent to a certain weight of gold. As part of this system, governments and central banks attempted to control the price of gold by setting values at which they would exchange it for currency. For a long period the United States government set the price of gold at $20.67 per troy ounce ($664.56/kg) but in 1934 the price of gold was set at $35.00 per troy ounce ($1125.27/kg). By 1961 it was becoming hard to maintain this price, and a pool of US and European banks began to act together to defend the price against market forces. On March 17 1968, economic circumstances caused the collapse of the gold pool, and a two-tiered pricing scheme was established whereby gold was still used to settle international accounts at the old $35.00 per troy ounce ($1.13/g) but the price of gold on the private market was allowed to fluctuate; this two-tiered pricing system was abandoned in 1975 when the price of gold was left to find its free-market level. Central banks still hold historical gold reserves as a reserve asset although the level has generally been declining. The largest gold depository in the world is that of the U.S. Federal Reserve Bank, held at Fort Knox. Since 1968 the price of gold on the open market has ranged widely, with a record high of $850/oz ($27,300/kg) on 21 January 1980, to a low of $252.90/oz ($8,131/kg) on 21 June 1999 (London Fixing). Prices have risen to the $500/oz mark in late 2005, due to a depreciation of the US dollar and inflation due to rising energy costs.

Gold and the money supply

In January 1959 US M3 money supply was $288.8 billion, and the Official Gold Holdings of the United States was then 17,335.1 Tonnes, or about 557 million ounces (there are 32,150.7 Troy Ounces in a Tonne). That means that in 1959, there were $518 in circulation for every ounce of gold reserves held by the USA. Although the theoretical price should then have been $518 per ounce, the actual price, as fixed under the gold standard was only $35 an ounce. By August 2005, the US M3 money supply had risen to $9,873.9 billion, whilst at the same time the Official Gold Holdings of the United States had fallen to just 8,133.5 Tonnes, or about 261 million Troy Ounces. This means that today, in 2005, there are $37,831 in circulation for every ounce of gold held by the United States. The above numbers show the falling influence of gold in the monetary system of the world today. Goldbugs believe, or even hope, that one day gold's importance will return as the printing of paper money gets out of control and we end in a hyper-inflationary fiat money collapse.

Restrictions on gold ownership

Because of its use as a reserve store of value, the possession of gold is sometimes restricted or banned. Within the United States, the private possession of gold except as jewelry and coin collecting was banned between 1933 and 1975. President Franklin D. Roosevelt confiscated gold by [http://www.the-privateer.com/1933-gold-confiscation.html Executive Order 6102], and President Richard Nixon closed the gold window by which foreign countries could exchange American dollars for gold at a fixed rate.

Return of a Gold Standard?

In the first few years of the 21st century, reports started to circulate that Malaysia was planning a return to the gold standard -- to issue and use gold dinars as currency in international trade. The purported purpose of this move would be to reduce dependence on the United States dollar as a reserve currency, and to establish a non-debt-backed currency in accord with Islamic law against the charging of interest. [http://www.islamidag.dk/ulamaongold.html] Nonetheless, gold dinar currency has not yet emerged. [http://english.aljazeera.net/NR/exeres/E7515CEE-880E-492F-B225-A94E21D90D2B.htm] [http://www.mineweb.net/columns/american_notes/336075.htm]

Gold in investment portfolios

As a tangible investment gold is sometimes held as part of a portfolio because over the long term gold has an extensive history of maintaining its value. It has in the last century gained ground in relation to fiat currencies owing to inflation. Gold becomes particularly desirable in times of extremely weak confidence and during hyperinflation because gold maintains its value even as fiat money becomes worthless. People who enjoy investing in gold are known as goldbugs. Futures contracts based on gold currently trade on various exchanges around the world. In the US this occurs primarily on COMEX (Commodity Exchange) which is a subsidiary of the New York Mercantile Exchange. Speculation about the future price of gold and other commodities is carried on at COMEX. Recently, gold-based ETFs like [http://finance.yahoo.com/q?s=GLD GLD] have emerged as a more convenient investment vehicle. In some countries such as Switzerland, it is possible to hold physical gold as part of an investment portfolio, due to the absence of taxes and narrow bid-ask spreads, however in other countries portfolio managers sometimes hold gold shares or gold bullion securities as a proxy for the metal itself. Exchange Traded Funds such as Gold Bullion Securities are securities sponsored by the World Gold Council and which are fully backed up by allocated gold held by a custodian. The main Gold Bullion Securities are as follows:
- New York Stock Exchange (NYSE), Symbol:GLD (Streettracks Gold Shares, ISIN No. US8633071043)
- London Stock Exchange (LSE) Symbol GBS (Gold Bullion Securities ISIN No. GB00B00FHZ82)
- Euronext France Symbol:GBS (Gold Bullion Securities ISIN No. GB00B00FHZ82 )
- Australian Stock Exchange (ASX), Symbol:GOLD (Gold Bullion Securities ISIN No. AU00000GOLD7)
- Johannesburg Securities Exchange (JSE), Symbol:GLD (New Gold Debentures ISIN No. ZAE000060067 )

Occurrence

Exchange Traded Fund Due to its relative chemical inertness gold is usually found as the native metal or alloy. Occasionally large accumulations of native gold (also known as nuggets) occur but usually gold occurs as minute grains. These grains occur between mineral grain boundries or as inclusions within minerals. Common gold associations are quartz often as veins and sulfide minerals. The most common sulfide associations are pyrite, chalcopyrite, galena, sphalerite, arsenopyrite, stibnite and pyrrhotite. Rarer mineral associations are petzite, calaverite, sylvanite, muthmannite, nagyagite and krennerite. Gold is widely distributed in the Earth's crust at a background level of 0.03 g/1000 kg (0.03 ppm by weight). Hydrothermal ore deposits of gold occur in metamorphic rocks and igneous rocks; alluvial deposits and placer deposits originate from these sources. The primary source of gold is usually igneous rocks or surface concentrations. A deposit usually needs some form of secondary enrichment to form an economically viable ore deposit: either chemical or physical processes like erosion or solution or more generally metamorphism, which concentrates the gold in sulfide minerals or quartz. There are several primary deposit types, common ones are termed reef or vein. Primary deposits can be weathered and eroded, with most of the gold being transported into stream beds where it congregates with other heavy minerals to form placer deposits. In all these deposits the gold is in its native form. Another important ore type is in sedimentary black shale and limestone deposits containing finely disseminated gold and other platinum group metals. Gold occurs in sea water at 0.1 to 2 mg/t (0.1 to 2 ppb by weight) depending on sample location.

Production

ppb Economic gold extraction can be achieved from ore grades as little as 0.5 g/1000 kg (0.5 ppm) on average in large easily mined deposits, typical ore grades in open-pit mines are 1–5 g/1000 kg (1-5 ppm), ore grades in underground or hard rock mines are usually at least 3 g/1000 kg (3 ppm) on average. Ore grades of 30 g/1000 kg (30 ppm) are usually needed before gold is visible to the naked eye, therefore in most gold mines you will not see any gold. It is claimed, that all the gold that has been mined throughout the history of mankind could be incorporated in a solid ball with a diameter of 27 metres. metre Since the 1880s South Africa has been the source for a large proportion of the world's gold supply. Production in 1970 accounted for 79% of the world supply, producing about 1,000 tonnes, however production in 2004 was 342 tonnes. This decline was due to the increasing difficulty of extraction and changing economic factors effecting the industry in South Africa. The city of Johannesburg was built atop the world's greatest gold finds. Gold fields in the Orange Free State and the Transvaal are deep and require the world's deepest mines. The Second Boer War of 1899–1901 between the British Empire and the white Boers was at least partly over the rights of miners and possession of the gold wealth in South Africa. Other major producers are Canada, United States and Western Australia. Mines in South Dakota and Nevada supply two-thirds of gold used in the United States. Siberian regions of the USSR also used to be significant in the global gold mining industry. Kolar Gold Fields in India is another example of a city being built on the greatest gold deposits in India. In South America, the controversial project Pascua Lama aims at exploitation of rich fields in the high mountains of Atacama, at the border between Chile and Argentina. The idea of producing gold out of lesser metals or other cheap substances has fascinated people throughout the centuries. Scientists, kings and charlatans obsessed with the secret art of alchemy accidentally invented practically useful materials (e.g. porcelain), while searching in vain for the philosopher's stone, which was supposed to turn mercury into gold. Modern science has since proven the impossibility of making gold from other elements via chemical reactions. However, it is possible to obtain infinitesimally small amounts of gold by artificial nuclear transformations in particle accelerators The gold isotopes produced would likely be radioactive. No economically feasible method to manufacture gold artificially has been found and published yet. The possibility of cheap man-made gold would have unforeseen economic and political consequences.

Compounds/isotopes

Although gold is a noble metal, it can form many compounds, auric chloride (AuCl₃) and chlorauric acid (HAuCl₄) being the most common. Gold compounds can be aurous (univalent, +1) or auric (trivalent, +3). Gold also can under extreme conditions form a +5 state with fluorine (gold pentafluoride, AuF₅), as well as (unusually for a metal), a -1 state. Such compounds containing the Au^- anion are called aurides and include caesium auride, CsAu, rubidium auride, RbAu, and tetramethylammonium auride, (CH₃)₄N⁺ Au^-. Gold also forms:
- The AuCl₄^- ion after dissolving in aqua regia
- Gold halides (F,Cl,Br,I)
- Gold chalcogenides (O, S, Se,Te)
- Gold cluster compounds
- Gold hydrazide: an olive-green powder, AuN₂H₃, one of several explosive compounds known archaically as aurum fulminans There is only one stable isotope of gold, and 18 radioisotopes with Au-195 being the most stable with a half-life of 186 days.

Precautions

The human body does not absorb gold very well, thus compounds of gold are not normally very toxic. Liver and kidney damage has, however, been reported for up to 50% of arthritis patients treated with gold-containing drugs. Gold used in dentistry is widely regarded as the safest form of restorative material, as well as the most successful.

Symbolism

Gold has been associated with the extremities of utmost evil and great sanctity throughout history. The Golden Calf is a widely-recognised symbol of idolatry and revolt against God; concentration camp guards removed the golden teeth from the mouths of gassed Holocaust victims. In Communist propaganda, the golden pocket watch and its fastening golden chain were the characteristic accessories of the class enemy, the bourgeois and the industrial tycoons. On the other hand, eminent orators such as John Chrysostom were said to have a mouth of gold with a silver tongue. Gold is associated with notable anniversaries, particularly in a 50 year cycle, such as a golden wedding anniversary, golden jubilee, etc. Great human achievements are frequently rewarded with gold, in the form of medals and decorations. Winners of races and prizes are usually awarded the gold medal (such as the Olympic Games and the Nobel Prize), while many award statues are depicted in gold (such as the Academy Awards, the Emmy Awards and the British Academy Film Awards). In the software development cycle "going gold" means releasing a version that is ready for distribution to customers, rather than a buggy beta version. Medieval kings were inaugurated under the signs of sacred oil and a golden crown, the latter symbolizing the eternal shining light of heaven and thus a Christian king's divinely inspired authority. Wedding rings are traditionally made of gold; since it is long-lasting and unaffected by the passage of time, it is considered a suitable material for everyday wear as well as a metaphor for the relationship. In Orthodox Christianity, the wedded couple is adorned with a golden crown during the ceremony, an amalgamation of symbolic rites. The symbolic value of gold varies wildly around the world, even within geographic regions. For example, gold is quite common in Turkey but considered a most valuable gift in Sicily.

References

- [http://periodic.lanl.gov/elements/79.html Los Alamos National Laboratory – Gold]
- [http://www.infoplease.com/ce6/sci/A0821152.html The Columbia Electronic Encyclopedia, 6th ed]

External links

- [http://www.webelements.com/webelements/elements/text/Au/index.html WebElements.com – Gold] (also used as a reference)
- [http://mineral.galleries.com/minerals/elements/gold/gold.htm Mineral Galleries - Native Gold]
- [http://www.lateralscience.co.uk/gold/auriferous.html Getting Gold 1898 book]
- Gold Category:Chemical elements Category:Transition metals Category:Numismatics Category:Historical trading items ms:Emas ja:金 simple:Gold th:ทองคำ

Ivory

Ivory is a hard, white, opaque substance that is the bulk of the teeth and tusks of animals such as the elephant, hippopotamus, walrus, mammoth, etc. Prior to the introduction of plastics, it was used for billiard balls, piano keys, buttons and ornamental items. The word "ivory" was traditionally applied to the tusks of elephants. Plastics have been viewed by piano purists as an inferior ivory substitute on piano keys, although other recently developed materials more closely resemble the feel of real ivory.

Structure

The chemical structure of the teeth and tusks of mammals is the same regardless of the species of origin, and the trade in certain teeth and tusks other than elephant is well established and widespread. Therefore, "ivory" can correctly be used to describe any mammalian teeth or tusks of commercial interest which is large enough to be carved or scrimshawed.

Teeth and tusks

scrimshaw Teeth and tusks have the same origins. Teeth are specialized structures adapted for food mastication. Tusks, which are extremely large teeth projecting beyond the lips, have evolved from teeth and give certain species an evolutionary advantage. The teeth of most mammals consists of a root and the tusk proper. Teeth and tusks have the same physical structures: pulp cavity, dentine, cementum and enamel. The innermost area is the pulp cavity. The pulp cavity is an empty space within the tooth that conforms to the shape of the pulp. Odontoblasts line the pulp cavity and are responsible for the production of dentine. Dentine, which is the main component of carved ivory objects, forms a layer of consistent thickness around the pulp cavity and comprises the bulk of the tooth and tusk. Dentine is a mineralized connective tissue with an organic matrix of collagenous proteins. The inorganic component of dentine consists of dahllite. Dentine contains a microscopic structure called dentinal tubules which are micro-canals that radiate outward through the dentine from the pulp cavity to the exterior cementum border. These canals have different configurations in different ivories and their diameter ranges between 0.8 and 2.2 micrometres. Their length is dictated by the radius of the tusk. The three dimensional configuration of the dentinal tubules is under genetic control and is therefore a characteristic unique to the order. Tooth and tusk ivory can be carved into an almost infinite variety of shapes and objects. A small example of carved ivory objects are small statuary, netsukes, jewelry, flatware handles, furniture inlays, and piano keys. Additionally, warthog tusks, and teeth from sperm whales, orcas and hippos can also be scrimshawed or superficially carved, thus retaining their morphologically recognizable shapes.

Availablity

orca Due to the rapid decline in the populations of the animals that produce it, the importation and sale of ivory in many countries is banned or severely restricted. Much of the decline in population is due to poachers during and before the 1980s. Since the worldwide ivory trade ban in 1989 there have been ups and downs in elephant populations, and ivory trade as bans have been placed and lifted. Many African countries including Zimbabwe and South Africa claim that ivory trade is necessary—both to stimulate their economies and reduce elephant populations which are allegedly harming the environment. In 2002 the United Nations partially lifted the ban on ivory trade, allowing a few countries to export certain amounts of ivory. Yet, a 1999 study done by Oxford University found that less than one percent of the five-hundred million US dollars ivory sales generate ever reach Africans; most of it goes to middlemen and vendors, so the effectiveness of the policy is in question. Kenya, which saw its elephant populations plummet in the decade preceding the 1989 ban, claims that legalizing ivory trade anywhere in Africa will endanger elephants everywhere in Africa as poachers would attempt to launder their illegal ivory with legal stockpiles. Trade in the ivory from the tusks of dead mammoths has occurred for 300 years and continues to be legal. Mammoth ivory is used today to make handcrafted knives and similar implements. A species of hard nut is gaining popularity as a replacement for ivory, although its size limits its usability. It is sometimes called vegetable ivory, or tagua, and is the seed endosperm of the ivory nut palm commonly found in coastal rainforests of Ecuador and Peru. [http://www.cnn.com/2005/TECH/science/04/26/vegivory/index.html]

Types of ivory

- Elephant and mammoth ivory from the tusks of bull elephants and mammoths.
- Walrus ivory from the tusks of a bull walrus.
- Sperm Whale and Killer Whale ivory
- Narwhal ivory
- Hippopotamus ivory
- Warthog ivory
- Elk Ivory from the bugling teeth of bull elk. So-called hornbill ivory, derived from a bird, is not true ivory but resembles it in some ways. Category:Art materials ja:象牙

Chryselephantine

Chryselephantine (from Greek chrysos, “gold,” and elephantinos, “ivory”), the architectural term given to statues which were built up on a wooden core, with ivory representing the flesh and gold the drapery. The two most well known examples are those scuplted by Pheidias of the statue of Athena (known as the "Athena Polias", where Athena is depicted in a warrior-like fashion and driving a war chariot) in the Parthenon and of Zeus in the temple at Olympia.

References

Wood

:This article describes the material produced by trees. For other uses, see Wood (disambiguation). Wood (disambiguation)]] Wood derives from woody plants, notably trees but also shrubs. Wood from the latter is only produced in small sizes, reducing the diversity of uses. Wood is a hygroscopic, cellular and anisotropic material. Dry wood is composed of fibers of cellulose (40%–50%) and hemicellulose (20%–30%) held together by lignin (25%–30%). Wood is the xylem tissue of the plant.
Uses
xylems.]] Wood has been used by man for millennia for many purposes, being many things to many people. One of its primary uses is as fuel. It may also be used as a material, for making artworks, boats, buildings, furniture, ships, tools, weapons, etc. Wood has been an important construction material since humans began building shelters, and remains in plentiful use today. Construction wood is commonly known as timber in International English, and lumber in American English. Wood may be broken down and be made into chipboard, engineered wood, hardboard, medium-density fibreboard (MDF), oriented strand board (OSB), paper or used to make other synthetic substances.
Formation
A tree increases in diameter by the formation, between the old wood and the inner bark, of new woody layers which envelop the entire stem, living branches, and roots. Where there are clear seasons, this can happen in a discrete pattern, leading to what is known as growth rings, as can be seen on the end of a log. If these seasons are annual these growth rings are annual rings. Where there is no seasonal difference growth rings are likely to be absent. Within a growth ring it may be possible to see two more or less well-defined parts. The part nearest the centre of the tree is more open textured and almost invariably lighter in color than that near the outer portion of the ring. The inner portion is formed early in the season, when growth is comparatively rapid; it is known as early wood or spring wood. The outer portion is the late wood or summer wood, being produced in the summer. In white pines there is not much contrast in the different parts of the ring, and as a result the wood is very uniform in texture and is easy to work. In hard pines, on the other hand, the late wood is very dense and is deep-colored, presenting a very decided contrast to the soft, straw-colored early wood. In ring-porous woods each season's growth is always well defined, because the large pores of the spring abut on the denser tissue of the fall before. In the diffuse-porous woods, the demarcation between rings is not always so clear and in some cases is almost (if not entirely) invisible to the unaided eye.
Knots
Knots are portions of branches included in the wood of the stem or larger branch. Branches generally originate at or near the pith (central axis) of a stem, and the living portion will increase in size through the addition of annual woody layers which are a continuation of those of the stem. The included portion is irregularly conical in shape with the tip at the pith. The fibre direction is at right angles or oblique to the grain of the stem, thus producing local cross grain. Note that a small knot may also be the result of a dormant bud. During the development of a tree the lower limbs die, but may persist for a time--often for years. Subsequent layers of growth of the stem are no longer intimately joined with the dead limb, but are laid around it. Hence dead branches produce knots which are nothing more than pegs in a hole, and likely to drop out after the tree has been sawn. In grading lumber and structural timber, knots are classified according to their form, size, soundness, and the firmness with which they are held in place. Knots materially affect checking (cracking) and warping, ease in working, and cleavability of timber. They are defects which weaken timber and depreciate its value for structural purposes where strength is an important consideration. The weakening effect is much more serious where timber is subjected to bending and tension than where under compression. The extent to which knots affect the strength of a beam depends upon their position, size, number, direction of fibre, and condition. A knot on the upper side is compressed, while one on the lower side is subjected to tension. The knot, especially (as is often the case) if there is a season check in it, offers little resistance to this tensile stress. Small knots, however, may be so located in a beam along the neutral plane as actually to increase the strength by tending to prevent longitudinal shearing. Knots in a board or plank are least injurious when they extend through it at right angles to its broadest surface. Knots which occur near the ends of a beam do not weaken it. Sound knots which occur in the central portion one-fourth the height of the beam from either edge are not serious defects. Knots do not necessarily influence the stiffness of structural timber. Only defects of the most serious character affect the elastic limit of beams. Stiffness and elastic strength are more dependent upon the quality of the wood fibre than upon defects in the beam. The effect of knots is to reduce the difference between the fibre stress at elastic limit and the modulus of rupture of beams. The breaking strength is very susceptible to defects. Sound knots do not weaken wood when subject to compression parallel to the grain. For some purposes, e.g. wall panelling, knots are considered a plus as they add visual texture to the wood, giving it a more interesting appearance.
Heartwood and sapwood
grain (centre dark spot). The dark radial lines are small knots.]] Examination of the end of a log of many species reveals a darker-colored inner portion, called the heartwood or duramen, surrounded by a lighter-colored zone called the sapwood. In some instances this distinction in color is very marked; in others, the contrast is slight, so that it is not always easy to tell where one leaves off and the other begins. The color of fresh sapwood is always light, sometimes nearly white, but more often with a decided tinge of yellow or brown. Sapwood is comparatively new wood, comprising living cells in the growing tree. All wood in a tree is first formed as sapwood. Its principal functions are to conduct water from the roots to the leaves and to store up and give back according to the season the food prepared in the leaves. The more leaves a tree bears and the more vigorous its growth, the larger the volume of sapwood required. Hence trees making rapid growth in the open have thicker sapwood for their size than trees of the same species growing in dense forests. Sometimes trees grown in the open may become of considerable size, 30 cm or more in diameter, before any heartwood begins to form, for example, in second-growth hickory, or open-grown pines. As a tree increases in age and diameter an inner portion of the sapwood becomes inactive and finally ceases to function, as the cells die. This inert or dead portion is called heartwood. Its name derives solely from its position and not from any vital importance to the tree. This is shown by the fact that a tree can thrive with its heart completely decayed. Some species begin to form heartwood very early in life, so having only a thin layer of live sapwood, while in others the change comes slowly. Thin sapwood is characteristic of such trees as chestnut, black locust, mulberry, osage-orange, and sassafras, while in maple, ash, hickory, hackberry, beech, and pine, thick sapwood is the rule. There is no definite relation between the annual rings of growth and the amount of sapwood. Within the same species the cross-sectional area of the sapwood is very roughly proportional to the size of the crown of the tree. If the rings are narrow, more of them are required than where they are wide. As the tree gets larger, the sapwood must necessarily become thinner or increase materially in volume. Sapwood is thicker in the upper portion of the trunk of a tree than near the base, because the age and the diameter of the upper sections are less. When a tree is very young it is covered with limbs almost, if not entirely, to the ground, but as it grows older some or all of them will eventually die and be broken off. Subsequent growth of wood may completely conceal the stubs which will however remain as knots. No matter how smooth and clear a log is on the outside, it is more or less knotty near the middle. Consequently the sapwood of an old tree, and particularly of a forest-grown tree, will be freer from knots than the heartwood. Since in most uses of wood, knots are defects that weaken the timber and interfere with its ease of working and other properties, it follows that sapwood, because of its position in the tree, may have certain advantages over heartwood. It is remarkable that the inner heartwood of old trees remains as sound as it usually does, since in many cases it is hundreds of years, and in a few instances thousands of years, old. Every broken limb or root, or deep wound from fire, insects, or falling timber, may afford an entrance for decay, which, once started, may penetrate to all parts of the trunk. The larvae of many insects bore into the trees and their tunnels remain indefinitely as sources of weakness. Whatever advantages, however, that sapwood may have in this connection are due solely to its relative age and position. If a tree grows all its life in the open and the conditions of soil and site remain unchanged, it will make its most rapid growth in youth, and gradually decline. The annual rings of growth are for many years quite wide, but later they become narrower and narrower. Since each succeeding ring is laid down on the outside of the wood previously formed, it follows that unless a tree materially increases its production of wood from year to year, the rings must necessarily become thinner as the trunk gets wider. As a tree reaches maturity its crown becomes more open and the annual wood production is lessened, thereby reducing still more the width of the growth rings. In the case of forest-grown trees so much depends upon the competition of the trees in their struggle for light and nourishment that periods of rapid and slow growth may alternate. Some trees, such as southern oaks, maintain the same width of ring for hundreds of years. Upon the whole, however, as a tree gets larger in diameter the width of the growth rings decreases. There may be decided differences in the grain of heartwood and sapwood cut from a large tree, particularly one that is mature. In some trees, the wood laid on late in the life of a tree is softer, lighter, weaker, and more even-textured than that produced earlier, but in other species, the reverse applies. In a large log the sapwood, because of the time in the life of the tree when it was grown, may be inferior in hardness, strength, and toughness to equally sound heartwood from the same log.
Different woods
There is a strong relationship between the properties of wood and the properties of the particular tree that yielded it. For every trees species there is a range of density for the wood it yields. There is a rough correlation between density of a wood and its strength (mechanical properties). For example, while mahogany is a medium-dense hardwood which is excellent for fine furniture crafting, balsa is light, making it useful for model building. The densest wood may be black ironwood. Wood is commonly classified as either softwood or hardwood. The wood from conifers (e.g. pine) is called softwood, and the wood from broad-leaved trees (e.g. oak) is called hardwood. These names are a bit misleading, as hardwoods are not necessarily hard, and softwoods are not necessarily soft. The well-known balsa (a hardwood) is actually softer than any commercial softwood. Conversely, some softwoods (e.g. yew) are harder than most hardwoods.
Color
In species which show a distinct difference between heartwood and sapwood the natural color of heartwood is usually darker than that of the sapwood, and very frequently the contrast is conspicuous. This is produced by deposits in the heartwood of various materials resulting from the process of growth, increased possibly by oxidation and other chemical changes, which usually have little or no appreciable effect on the mechanical properties of the wood. Some experiments on very resinous Longleaf Pine specimens, however, indicate an increase in strength. This is due to the resin which increases the strength when dry. Such resin-saturated heartwood is called "fat lighter". Structures built of fat lighter are almost impervious to rot and termites; however they are very flammable. Stumps of old longleaf pines are often dug, split into small pieces and sold as kindling for fires. Stumps thus dug may actually remain a century or more since being cut. Spruce impregnated with crude resin and dried is also greatly increased in strength thereby. Spruce Since the late wood of a growth ring is usually darker in color than the early wood, this fact may be used in judging the density, and therefore the hardness and strength of the material. This is particularly the case with coniferous woods. In ring-porous woods the vessels of the early wood not infrequently appear on a finished surface as darker than the denser late wood, though on cross sections of heartwood the reverse is commonly true. Except in the manner just stated the color of wood is no indication of strength. Abnormal discoloration of wood often denotes a diseased condition, indicating unsoundness. The black check in western hemlock is the result of insect attacks. The reddish-brown streaks so common in hickory and certain other woods are mostly the result of injury by birds. The discoloration is merely an indication of an injury, and in all probability does not of itself affect the properties of the wood. Certain rot-producing fungi impart to wood characteristic colors which thus become symptomatic of weakness. Ordinary sap-staining is due to fungous growth, but does not necessarily produce a weakening effect.
Structure
fungi (parquet).]] In coniferous or softwood species the wood cells are mostly of one kind, tracheids, and as a result the material is much more uniform in structure than that of most hardwoods. There are no vessels ("pores") in coniferous wood such as one sees so prominently in oak and ash, for example. The structure of the hardwoods is more complex. They are more or less filled with vessels: in some cases (oak, chestnut, ash) quite large and distinct, in others (buckeye, poplar, willow) too small to be seen plainly without a small hand lens. In discussing such woods it is customary to divide them into two large classes, ring-porous and diffuse-porous. In ring-porous species, such as ash, black locust, catalpa, chestnut, elm, hickory, mulberry, and oak, the larger vessels or pores (as cross sections of vessels are called) are localized in the part of the growth ring formed in spring, thus forming a region of more or less open and porous tissue. The rest of the ring, produced in summer, is made up of smaller vessels and a much greater proportion of wood fibres. These fibres are the elements which give strength and toughness to wood, while the vessels are a source of weakness. In diffuse-porous woods the pores are scattered throughout the growth ring instead of being collected in a band or row. Examples of this kind of wood are basswood, birch, buckeye, maple, poplar, and willow. Some species, such as walnut and cherry, are on the border between the two classes, forming an intermediate group. If a heavy piece of pine is compared with a light specimen it will be seen at once that the heavier one contains a larger proportion of late wood than the other, and is therefore considerably darker. The late wood of all species is denser than that formed early in the season, hence the greater the proportion of late wood the greater the density and strength. When examined under a microscope the cells of the late wood are seen to be very thick-walled and with very small cavities, while those formed first in the season have thin walls and large cavities. The strength is in the walls, not the cavities. In choosing a piece of pine where strength or stiffness is the important consideration, the principal thing to observe is the comparative amounts of early and late wood. The width of ring is not nearly so important as the proportion of the late wood in the ring. It is not only the proportion of late wood, but also its quality, that counts. In specimens that show a very large proportion of late wood it may be noticeably more porous and weigh considerably less than the late wood in pieces that contain but little. One can judge comparative density, and therefore to some extent weight and strength, by visual inspection. cherry No satisfactory explanation can as yet be given for the real causes underlying the formation of early and late wood. Several factors may be involved. In conifers, at least, rate of growth alone does not determine the proportion of the two portions of the ring, for in some cases the wood of slow growth is very hard and heavy, while in others the opposite is true. The quality of the site where the tree grows undoubtedly affects the character of the wood formed, though it is not possible to formulate a rule governing it. In general, however, it may be said that where strength or ease of working is essential, woods of moderate to slow growth should be chosen. But in choosing a particular specimen it is not the width of ring, but the proportion and character of the late wood which should govern. In the case of the ring-porous hardwoods there seems to exist a pretty definite relation between the rate of growth o