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Despite being sharper, prismatic obsidian is also considerably more brittle than steel; obsidian blades of the type used on the macuahuitl tended to shatter on impact with other obsidian blades, steel swords or plate armour. Obsidian blades also have difficulty penetrating European mail. The thin, replaceable blades used on the macuahuitl were ...
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.
Obsidian can be used to make extremely sharp knives, and obsidian blades are a type of glass knife made using naturally occurring obsidian instead of manufactured glass. Obsidian is used by some surgeons for scalpel blades, although this is not approved by the US Food and Drug Administration (FDA) for use on humans. [61]
Obsidian scalpels have been investigated for use in delicate surgery. [35] Pumice, also typically of rhyolitic composition, finds important uses as an abrasive, in concrete, [36] and as a soil amendment. [37] Rhyolitic tuff was used extensively for construction in ancient Rome [38] and has been used in construction in modern Europe. [21]: 138
Obsidian is rare, though sizable obsidian (even large boulders) are common at Newberry Volcanic monument in central Oregon. The reason it is rare is because it forms from high-silica lava, must cool quickly before crystals can form, and must be free of volatiles.
Pages in category "Obsidian" The following 17 pages are in this category, out of 17 total. This list may not reflect recent changes. * Obsidian; A. Apache tears; B.