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Smoky quartz is a brownish grey, translucent variety of quartz that ranges in clarity from almost complete transparency to an almost-opaque brownish-gray or black crystals. [6] The color of smoky quartz is produced when natural radiation, emitted from the surrounding rock, activates color centers around aluminum impurities within the ...
Nephrite can be found in a translucent white to very light yellow form which is known in China as mutton fat jade, [1] in an opaque white to very light brown or gray which is known as chicken bone jade, [1] as well as in a variety of green colors. Western Canada is the principal source of modern lapidary nephrite. [2]
The appearance of a spot usually indicates an inclusion of uncrystallized carbon, but a cloudy carbon flaw is indicative of improper or irregular crystallization. [2] Carbon flaws can also appear as small, fuzzy dots, somewhere between a speck and a cloud. Another common carbon flaw appears as a black shard or needle through the stone.
Smoky quartz is a gray, translucent version of quartz. It ranges in clarity from almost complete transparency to a brownish-gray crystal that is almost opaque. Some can also be black. The translucency results from natural irradiation acting on minute traces of aluminum in the crystal structure. [54]
Grey, red, black, altered white/tan, flow-banded pumice dacite. In hand specimen, many of the hornblende and biotite dacites are grey or pale brown and yellow rocks with white feldspars, and black crystals of biotite and hornblende. Other dacites, especially pyroxene-bearing dacites, are darker colored. [4]
Andradite is a mineral species of the garnet group.It is a nesosilicate, with formula Ca 3 Fe 2 Si 3 O 12.. Andradite includes three varieties: Colophonite: a historical variety found in the Scandinavian islands, brownish or reddish in color, often opaque or translucent.
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The dull grey-black color of tenorite contrasts sharply with the often intergrown blue chrysocolla. Cuprite, native copper and Fe–Mn oxides also occur in this environment. [2] In addition to the hydrothermal, tenorite also occurs as a volcanic sublimate from Vesuvius, Campania, and Etna, Sicily, Italy.