Cryptocrystalline

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). The quartz crystals in chalcedony are so tiny that they cannot be distinguished with the naked eye.[2]

See also

References

  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.
  2. ^ Jesse, Dorothea (5 July 2024). "How Hard is Agate on the Mohs Scale". Retrieved July 5, 2024.


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