Cryptocrystalline is arock texture made up of such minutecrystals that its crystalline nature is only vaguely revealed even microscopically[1] inthin section by transmittedpolarized light. Among thesedimentary rocks,chert andflint are cryptocrystalline.Carbonado, a form of diamond, is also cryptocrystalline.Volcanic rocks, especially of the felsic type such asfelsites andrhyolites, may have a cryptocrystallinegroundmass as distinguished from pureobsidian (felsic) ortachylyte (mafic), which are natural rockglasses.Agate andonyx are examples of cryptocrystallinesilica (chalcedony). Thequartz crystals in chalcedony are so tiny that they cannot be distinguished with the naked eye.[2]
