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Until now, the earliest occurrences were in Catalonian contexts dated to the transition between the fifth and the fourth millennia BC: a core, a blade and four bladelets, all of which have been traced to a source known as ‘Sardinian A’ (Terradas et al. In Iberia, however, the Early Neolithic obsidian trail eventually vanishes. Reference Isern, Zilhão, Fort and Ammerman2017).
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For example, variation with distance to source in the number of obsidian finds and the representation of the different phases of its chaîne opératoire have been used to support the concept of maritime pioneer colonisation as the primary mode of dispersal of the Neolithic package along the northern shores of Western Mediterranean Europe (Lugliè Reference Lugliè, Moncel and Fröhlich2009 Zilhão Reference Zilhão2014 Isern et al. Obsidian sourcing has also been instrumental in debates concerning Tardiglacial/Early Holocene sea voyaging and the tempo and mode of the emergence of farming in the Mediterranean Basin (Ammerman & Davis Reference Ammerman and Davis2013–2014). Reference Dobrescu, Tuffreau and Bonsall2018). Reference Le Bourdonnec2012 Dobrescu et al.
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In Eastern Europe and Western Asia examples of obsidian use are known from the Middle and the Upper Palaeolithic of Transcaucasia and the Carpathians, highlighting raw material movements across distances in excess of 100km (Le Bourdonnec et al. Moreover, as the provenance of raw obsidian can be chemically finger-printed to specific sources, it is also a valuable material for tracing patterns of prehistoric mobility and exchange. Its well-developed conchoidal fracture and the hardness and sharpness of its knapped edges explain why, where available, this silica-rich volcanic glass was so widely used. Utah is a major source of the snowflake variety.Obsidian was a raw material of choice for Stone Age peoples worldwide. Arizona, Colorado, and California each have several productive localities. The United States is a major source of gem-quality material. You might encounter artificial or manufactured blue, green, or red glass pieces passed off as natural obsidians with these rare colors. See our glass gem listing for more information. The specific gravity range of both chalcedony and schorl overlaps with that of obsidian, but an RI test should separate them. However, standard gemological tests should distinguish them. Some commonly encountered natural gemstones that may be substituted or confused with obsidians are jet, chalcedony, and schorl (black tourmaline). Obsidians can have a moderate to very strong reaction. Obsidians may also have straight banding and needles, two more telltale signs of natural origins.Īlthough not a definitive test, checking for magnetic reactions may help confirm a glass piece as natural. Due to the difference in their refractive indices (RI), these will usually stand out in high relief when examined under magnification. Natural obsidians may contain some specific inclusions, such as crystallites, that help distinguish them from artificial glass. None, but crystal inclusions in obsidian may be birefringent.Ģ.25-3.00. Basalt glass may be splintery.Īmorphous usually as rounded masses ejected in volcanic eruptions, as small broken pieces, fine, hairlike filaments (for example, Pele’s Hair), and as flows. Iridescence noted: gold, silver, blue, violet, green, and combinations of these colors, due to inclusions of minute bubbles that reflect light.Ĭonchoidal (best example of this type of fracture). Green, blue, and reddish stones (transparent) are very rare. Protogenic silica minerals crystallizing in obsidian may be white and resemble snowflakes, hence the term snowflake obsidian.īlack gray, banded with brown streaks. Needlelike inclusions may give a silvery sheen. Bubbles are often in parallel arrangement. Obsidian is found in areas of present and former volcanic activity.Įlongated, torpedo-shaped bubbles, round bubbles, teardrop-shaped bubbles. Īfter Obsius, an explorer who discovered this material in Ethiopia, according to the Ancient Roman naturalist Pliny the Elder. Variable composition: SiO 2 approximately 66-72% + oxides of Ca, Na, K, and so forth. Since prehistoric times, people have used this material to make jewelry and carvings as well as practical objects, like knives.Īpache Tears, Fire Obsidian, Mahogany Obsidian, Rainbow Obsidian, Sheen Obsidian, Snowflake Obsidian Obsidian is the most common form of natural glass and occurs in many attractive varieties.