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Mantle ("The Paracas Textile"), 100-300 C.E. Cotton, camelid fiber, textile: Brooklyn Museum Detail of one shaman showing knife and head The Paracas textiles were found at a necropolis in Peru in the 1920s.
The source of obsidian for cultures inhabiting the territory of and around Greece was the island of Milos; the Starčevo–Körös–Criș culture obtained obsidian from sources in Hungary and Slovakia, while the Cardium-Impresso cultural complex acquired obsidian from the island outcrops of the central Mediterranean.
Eclogite-derived melts may be common in the mantle, and contribute to volcanic regions where unusually large volumes of magma are erupted. [18] The eclogite melt may then react with enclosing peridotite to produce pyroxenite , which in turn melts to produce basalt.
Obsidian projectile point.. Obsidian is a naturally formed volcanic glass that was an important part of the material culture of Pre-Columbian Mesoamerica.Obsidian was a highly integrated part of daily and ritual life, and its widespread and varied use may be a significant contributor to Mesoamerica's lack of metallurgy.
An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed, and often emplaced onto continental crustal rocks. The Greek word ὄφις, ophis (snake) is found in the name of ophiolites, because of the superficial texture of some of them. Serpentinite especially evokes a snakeskin.
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.
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 ...
Although helenite and obsidian are both forms of glass, helenite differs from obsidian in that it is man-made. The stone has been marketed by the jewelry industry because of its emerald-like color, good refractive index, although its durability is low. It has a hardness of just 5 to 5 ½ and chips about as easily as obsidian or window glass.