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  2. Volcanic glass - Wikipedia

    en.wikipedia.org/wiki/Volcanic_glass

    Volcanic glass is the amorphous (uncrystallized) product of rapidly cooling magma. Like all types of glass, it is a state of matter intermediate between the closely ...

  3. Tachylite - Wikipedia

    en.wikipedia.org/wiki/Tachylite

    Tachylite (/ ˈ t æ k ə l aɪ t / TAK-ə-lyte; also spelled tachylyte) is a form of basaltic volcanic glass. This glass is formed naturally by the rapid cooling of molten basalt. It is a type of mafic igneous rock that is decomposable by acids and readily fusible. [citation needed] The color is a black or dark-brown, and it has a greasy ...

  4. Helenite - Wikipedia

    en.wikipedia.org/wiki/Helenite

    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.

  5. Obsidian - Wikipedia

    en.wikipedia.org/wiki/Obsidian

    Obsidian (/ ə b ˈ s ɪ d i. ən, ɒ b-/ əb-SID-ee-ən ob-) [5] is a naturally occurring volcanic glass formed when lava extruded from a volcano cools rapidly with minimal crystal growth. It is an igneous rock . [ 6 ]

  6. Perlite - Wikipedia

    en.wikipedia.org/wiki/Perlite

    Perlite is an amorphous volcanic glass that has a relatively high water content, typically formed by the hydration of obsidian. It occurs naturally and has the unusual property of greatly expanding when heated sufficiently.

  7. Sideromelane - Wikipedia

    en.wikipedia.org/wiki/Sideromelane

    Sideromelane from Hawaii. Sideromelane is a vitreous basaltic volcanic glass, usually occurring in palagonite tuff, [1] for which it is characteristic. It is a less common form of tachylite, with which it usually occurs together; however it lacks the iron oxide crystals dispersed in the glass, and therefore appears transparent and pure, with yellow-brown color, instead of tachylite opaque ...

  8. Apache tears - Wikipedia

    en.wikipedia.org/wiki/Apache_tears

    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 ...

  9. Komatiite - Wikipedia

    en.wikipedia.org/wiki/Komatiite

    The rarely preserved flow top breccia and pillow margin zones in some komatiite flows are essentially volcanic glass, quenched in contact with overlying water or air. Because they are rapidly cooled, they represent the liquid composition of the komatiites, and thus record an anhydrous MgO content of up to 32% MgO.