(n.) A cryptocrystalline, translucent variety of quartz, having usually a whitish color, and a luster nearly like wax.
Example Sentences:
(1) The free silicic oxide is presented by low-temperature crystobalite and quartz, more rarely opal and chalcedony.
Chert
Definition:
(n.) An impure, massive, flintlike quartz or hornstone, of a dull color.
Example Sentences:
(1) Occurrence of well-preserved rod-shaped and coccoid bacteria in the Precambrian Gunflint chert (1.9 x 10(9) years old) has been demonstrated by electron microscopy.
(2) In order to evaluate the degree of morphological preservation of erythrocytes in bloodstains, an accidental human blood smear on white chert and several experimental bloodstains on hard substrates (the same stone-white chert; another type of stone-graywacke; a non-stone support-stainless steel), were stored in a room, in non-sterile and fluctuating conditions, for lengths of time ranging from 3 to 18 months.
(3) Large amounts of well preserved microfossils have been reported from the cherts of the Upper Proterozoic of the Bohemian Massif (Middle Europe).
(4) Two billion year old black chert lenses from the Duck Creek formation, northwestern Western Australia, contain abundant organically preserved microorganisms which are morphologically similar to fossils of approximately the same age from the Gunflint formation, Ontario.