Cryptocrystalline is a rock texture made up of such minute crystals that its crystalline nature is only vaguely revealed even microscopically[1] in thin section by transmitted polarized light. Among the sedimentary rocks, chert and flint are cryptocrystalline. Carbonado, a form of diamond, is also cryptocrystalline. Volcanic rocks, especially of the felsic type such as felsites and rhyolites, may have a cryptocrystalline groundmass as distinguished from pure obsidian (felsic) or tachylyte (mafic), which are natural rock glasses. Agate and onyx are examples of cryptocrystalline silica (chalcedony).

See also


  1. ^ American Geological Institute (1984). Bates, Robert Latimer; Jackson, Julia A. (eds.). Dictionary of geological terms (3rd ed.). Garden City, New York: Anchor Press/Doubleday. p. 120. ISBN 0385181000. OCLC 9412868.