Volcanic glass
Volcanic glass is the amorphous 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 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, a basaltic glass with relatively low silica content.
- Sideromelane, a less common form of 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, thin sheets and flakes of brownish-green to near-clear volcanic glass, usually basaltic.
