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volcanic rock

Definitions of volcanic rock
  1. noun
    extrusive igneous rock solidified near or on the surface of the Earth
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    types:
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    agglomerate
    volcanic rock consisting of large fragments fused together
    amygdaloid
    volcanic rock in which rounded cavities formed by expanding gas have subsequently become filled with mineral deposits
    dacite
    a grey volcanic rock containing plagioclase and quartz and other crystalline minerals
    basalt
    the commonest type of solidified lava; a dense dark grey fine-grained igneous rock that is composed chiefly of plagioclase feldspar and pyroxene
    volcanic glass
    a kind of natural glass produced when molten lava cools very rapidly
    lava
    rock that in its molten form (as magma) issues from volcanos; lava is what magma is called when it reaches the surface
    tufa, tuff
    hard volcanic rock composed of compacted volcanic ash
    obsidian
    acid or granitic glass formed by the rapid cooling of lava without crystallization; usually dark, but transparent in thin pieces
    pitchstone
    dark acid granitic glass
    tachylite
    a basic or basalt glass
    aa
    a dry form of lava resembling clinkers
    pahoehoe
    freely flowing lava
    pillow lava
    lava that hardened in rounded shapes suggestive of pillows; believed to result from underwater eruptions
    type of:
    igneous rock
    rock formed by the solidification of molten magma
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