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Some view Jade use in Mesoamerica as largely influenced by the conceptualization of the material as a rare and valued commodity among pre-Columbian Mesoamerican cultures, such as the Olmec, the Maya, and the various groups in the Valley of Mexico. Until the 21st century it was thought the only source from which the indigenous cultures could obtain jade was the Motagua River valley in Guatemala. In addition to being an elite good of highly symbolic use in the performance of ideological ritual the high pressure minerals that form the translucent rocks termed jades are much tougher and more damage resistant than slightly harder but far more brittle materials such as flint. This extreme durability makes fine grained or fibrous jadeite and nephrite in effect the 'steel' of neolithic technology. It was often worked or carved in a variety of ways, either as ornamental stones, a medium upon which hieroglyphs were inscribed, or shaped into figurines, weapons, and other objects. Many jade artifacts crafted by later Mesoamerican civilizations, appear cut from simple jade axes, implying that the earliest trade had a utilitarian component. The general term jade refers to two separate rock types. The first is called nephrite, a calcium and magnesium rich amphibole mineral. Nephrite does not exist in Mesoamerica. The second is jadeite, a pyroxene rich in sodium and aluminum. Variation in color is largely due to variation in trace element composition. In other words, the types of trace elements and their quantities affect the overall color of the material. The “Olmec Blue” jade owes its unique color to the presence of iron and titanium, while the more typical green jade’s color is due to the varying presence of sodium, aluminum, iron, and chromium. Translucence can vary as well, with specimens ranging form nearly clear to completely opaque. Among Mesoamerican archaeologists, "jade" is sometimes used in a manner that does not differentiate between jadeite and other similar-looking, relatively hard greenstones such as albitite, omphacite, chrysoprase, and quartzite.〔Pool (2007, p.150).〕 ==Sources in Mesoamerica== The archaeological search for the Mesoamerican jade sources, which were largely lost at the time of the Maya collapse, began in 1799 when Alexander von Humboldt started his geological research in the New World. Von Humboldt sought to determine whether or not Neolithic jadeite celts excavated from European Megalithic archaeological sites like Stonehenge and Carnac shared sources with the similar looking jade celts from Mesoamerica (they do not). The first discovery of in-situ jade quarries was made by Archeologist Mary Lou Ridinger in 1974.〔http://www.nytimes.com/1988/01/24/travel/a-mayan-past-a-latin-present-in-guatemala.html?pagewanted=2〕 Previous to this discovery, academic consensus had not been reached regarding the true source of jade used by the Maya and debate continued for some time after, though it is now accepted as the first conclusive discovery of the sources of jade that the Maya culture had used. Since the first discovery, Ridinger also discovered many varieties of Central American jadeite that had never before been seen, such as lilac jade and a variety of jadeite with pyrite inclusions.〔http://www.natchezdemocrat.com/1999/10/19/archaeologist-tells-story-of-lost-jade-mines/〕 From 1974 to 1996 the only documented source of jadeite in Mesoamerica was the lowland Motagua River valley. Research conducted by the Mesoamerican Jade Project of Harvard's Peabody Museum of Archaeology & Ethnology between 1977 and 2000 led to the identification of both the long lost 'Olmec Blue" mines, a discovery published by Mesoamerican Jade project Field Director Russell Seitz and his colleagues from the American Museum of Natural History in ''Antiquity'' in December 2001. They in addition conducted geochemical dating of several ancient Maya lode mines and alluvial sources in the mountainous areas on both sides of the Motagua. Following their exposure by the torrential rains of Hurricane Mitch in 1998, alluvial cobbles of blue jade were traced up a southern Motagua tributary, the Rio Tambor, to massive outcrops of fine grained translucent ' Olmec Blue' jadeite, at elevations of between 1200 and 3800 feet in the province of Jalapa, along a fault extending from Carrizal Grande to La Ceiba. Geochemical dating revealed that the southern deposits, including the archaeologically important translucent blue jade, were ~ 40 MA older that the coarse grained opaque jades mined for sale to tourists, or those from the higher elevations around a northern Motagua tributary, the Rio Blanco, where jadeite outcrops are found at elevations of up to an elevation of 6,000 feet and several of the ancient mining sites are connected by dry-laid stone paths. It is noteworthy that the richest 'Olmec Blue' source area, far from being in 'the Motagua Valley' lies about 50 km southwest of Copan. Since the Motagua becomes Guatemala's border with Honduras, Honduras may host alluvial jade as well. The rediscovered 'Olmec' jade is of the quality traded throughout formative Mesoamerica, reaching areas as distant as the Valley of Mexico and Costa Rica. While Pool notes that "for many years, it had been suggested that there might be another source in the Balsas River valley", p. 151 no such Mexican source has come to light; However, recent work has revealed that the high pressure-low temperature metamorphic rocks ( blueschist facies) hosting jade deposits in Guatemala also outcrop as jadeite boulder bearing serpentine melange deposits at several places in Cuba and Hispaniola, where the material was exploited by the Taino and Carib cultures. Jade artifacts, mainly pointed celts, apparently stemming from these Antillean sources have been excavated as far east as Antigua in the Windward Islands. Given the scope and duration of the regional tectonic processes that created and exhumed these jade deposits, they may well extend into Chiapas as well. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Jade use in Mesoamerica」の詳細全文を読む スポンサード リンク
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