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Obsidian artifacts are common at Tell Brak, one of the earliest Mesopotamian urban centers, dating to the late fifth millennium BC. [44] Obsidian was valued in Stone Age cultures because, like flint, it could be fractured to produce sharp blades or arrowheads in a process called knapping.
Apache tears are rounded pebbles of obsidian or "obsidianites" composed of black or dark-colored natural volcanic glass, usually of rhyolitic composition and bearing conchoidal fracture. Also known by the lithologic term marekanite , this variety of obsidian occurs as subrounded to subangular bodies up to about 2 in (51 mm) in diameter, often ...
Helenite, also known as Mount St. Helens obsidian, emerald obsidianite, and ruby obsidianite, is a glass made from the fused volcanic rock dust from Mount St. Helens and marketed as a gemstone. [ 1 ] [ 2 ] Helenite was first created accidentally after the eruption of Mount St. Helens in 1980 .
Most commonly, volcanic glass refers to obsidian, a rhyolitic glass with high silica (SiO 2) content. [7] Other types of volcanic glass include the following: Pumice, which is considered a glass because it has no crystal structure. Apache tears, a kind of nodular obsidian.
Prismatic blades are flaked from stone cores through pressure flaking or direct percussion. [2] This process results in a very standardized finished tool and waste assemblage. The most famous and most prevalent prismatic blade material is obsidian, as obsidian use was widespread in Mesoamerica, though chert, flint, and chalcedony blades are not ...
Flintknapping a stone tool. Knapping is the shaping of flint, chert, obsidian, or other conchoidal fracturing stone through the process of lithic reduction to manufacture stone tools, strikers for flintlock firearms, or to produce flat-faced stones for building or facing walls, and flushwork decoration.
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In the Late Postclassic (c. 1200–1521) obsidian came to be the stone of preference for fashioning mirrors in Central Mexico. [6] Broken pieces of raw obsidian were likely to have been used as mirrors as far back as the Preclassic but obsidian was not commonly ground and polished to manufacture mirrors until this period. [6]