The Collaborative International Dictionary
Volcanic \Vol*can"ic\, a. [Cf. F. volcanique, It. vulcanico.]
Of or pertaining to a volcano or volcanoes; as, volcanic heat.
Produced by a volcano, or, more generally, by igneous agencies; as, volcanic tufa.
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Changed or affected by the heat of a volcano.
Volcanic bomb, a mass ejected from a volcano, often of molten lava having a rounded form.
Volcanic cone, a hill, conical in form, built up of cinders, tufa, or lava, during volcanic eruptions.
Volcanic foci, the subterranean centers of volcanic action; the points beneath volcanoes where the causes producing volcanic phenomena are most active.
Volcanic glass, the vitreous form of lava, produced by sudden cooling; obsidian. See Obsidian.
Volcanic mud, fetid, sulphurous mud discharged by a volcano.
Volcanic rocks, rocks which have been produced from the discharges of volcanic matter, as the various kinds of basalt, trachyte, scoria, obsidian, etc., whether compact, scoriaceous, or vitreous.
WordNet
n. a kind of natural glass produced when molten lava cools very rapidly
Wikipedia
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. 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.
Usage examples of "volcanic glass".
Eveleen knew that the unmeasured tons of rock being spewed into the sky would be coming down soon, bringing with it a killing downblast that would send out lateral shock waves of volcanic glass shards to shred whatever wasn't being burned by the ash clouds.
Beside it on the table lay a ball of black volcanic glass, a gold ring, and a crude doll wrought of rag and twigs.
The weight of the volcanic glass pressed down as he shoveled it over the top of his head.
Obsidian is a volcanic glass formed by rapid cooling of liquid lava.
It was pristine, almost beautiful, except for a wide stain of sand hardened into dark volcanic glass, in the center of the garden between three standing stones.
The spears were crude weapons-hollow wooden shafts tipped with slivers of volcanic glass-but when a keen-edged harpoon grazed his Hank, Kaa lost half his air in a reflexive cry.