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.
Famous quotes containing the words volcanic and/or glass:
“Pity the planet, all joy gone
from this sweet volcanic cone;”
—Robert Lowell (19171977)
“A sudden violent jolt of it has been known to stop the victims watch, snap his suspenders and crack his glass eye right across.”
—Irvin S. Cobb (18761944)