Volcanic glass

Volcanic glass
A sand grain of volcanic glass under the petrographic microscope. Its amorphous nature makes it go extinct in cross-polarized light (bottom frame). Scale box in millimeters.

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 close-packed, highly ordered array of a crystal and the highly disordered array of gas.[1] Volcanic glass can refer to the interstitial, or matrix material in an aphanitic (fine grained) volcanic rock or can refer to any of several types of vitreous igneous rocks. Most commonly, it refers to obsidian, a rhyolitic glass with high silica content.

Other types of volcanic glass include:

  • Pumice, which is considered a glass because it has no crystal structure.
  • Apache tears, a kind of nodular obsidian.
  • Tachylite (also spelled tachylyte), a basaltic glass with relatively low silica content.
  • Sideromelane, a less common form tachylyte.
  • Palagonite, a basaltic glass with relatively low silica content.
  • Hyaloclastite, a hydrated tuff-like breccia of sideromelane and palagonite.
  • Pele's hair, threads or fibers of volcanic glass, usually basaltic.
  • Pele's tears, tear-like drops of volcanic glass, usually basaltic.
  • Limu o Pele (Pele's seaweed), thin sheets and flakes of brownish-green to near-clear volcanic glass, usually basaltic.

References

  1. ^ Bates and Jackson, 1984, Dictionary of Geological Terms, 3rd ed., Prepared by the American Geological Institute

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  • Volcanic glass — Volcanic Vol*can ic, a. [Cf. F. volcanique, It. vulcanico.] 1. Of or pertaining to a volcano or volcanoes; as, volcanic heat. [1913 Webster] 2. Produced by a volcano, or, more generally, by igneous agencies; as, volcanic tufa. [1913 Webster] 3.… …   The Collaborative International Dictionary of English

  • volcanic glass — n. natural glass, as obsidian, formed by the very rapid cooling of molten lava …   English World dictionary

  • volcanic glass — a natural glass produced when molten lava cools very rapidly; obsidian. [1830 40] * * * Any glassy rock formed from lava or magma that has a chemical composition close to that of granite. Such molten material may reach very low temperatures… …   Universalium

  • volcanic glass — noun a kind of natural glass produced when molten lava cools very rapidly • Hypernyms: ↑volcanic rock • Hyponyms: ↑obsidian, ↑pitchstone, ↑tachylite …   Useful english dictionary

  • volcanic glass — volcan′ic glass′ n. gel a natural glass produced when molten lava cools very rapidly; obsidian • Etymology: 1830–40 …   From formal English to slang

  • volcanic glass — noun Date: circa 1840 natural glass produced by the cooling of molten lava too rapidly to permit crystallization …   New Collegiate Dictionary

  • volcanic glass — /vɒlkænɪk ˈglas/ (say volkanik glahs) noun a natural glass produced when molten lava cools very rapidly; obsidian …   Australian-English dictionary

  • volcanic glass — noun another term for obsidian …   English new terms dictionary

  • Volcanic ash — consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions,United States Geological Survey. [http://volcanoes.usgs.gov/Hazards/What/Tephra/tephra.html Tephra: Volcanic Rock and Glass Fragments.] Retrieved… …   Wikipedia

  • Volcanic — Vol*can ic, a. [Cf. F. volcanique, It. vulcanico.] 1. Of or pertaining to a volcano or volcanoes; as, volcanic heat. [1913 Webster] 2. Produced by a volcano, or, more generally, by igneous agencies; as, volcanic tufa. [1913 Webster] 3. Changed or …   The Collaborative International Dictionary of English

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