Minerals smoky quartz

One of the commonest forms of hole-excess center imparts color to the minerals smoky quartz and amethyst. These minerals are forms of silica, containing aluminium as an impurity. The AP+ substitutes for 81 +, and to preserve charge neutrality equal amounts of H+ are incorporated into the crystal. The smoky purple color arises in the electron deficient [A104] group. It is formed when an electron is liberated from a neutral [A104] group by ionising radiation is trapped on one of the H+ ions present. Other hole centers have been described in a variety of crystals. 

Quartz is the most common mineral in the Earth s crust. It occurs in a wide variety of forms, colors, and lusters, but other properties are generally consistent for all specimens. All quartz has the same basic chemical formula, silicon dioxide (SiC ). It has a hardness of 7, and a distinctive conchoidal fracture. The color and translucency of quartz can be affected by a disruption of the molecular structure, as in smoky quartz, or by the inclusions of tiny amounts of other elements or minerals. In some classifications, quartz is listed with the oxides, but it is most often placed with the silicates. 

Transitions between electronic energy levels in imperfect crystals. The colours of some minerals and semi-precious gems, notably Cairngorms or smoky quartz where colour comes from defects in the quartz lattice caused by... 

Ore minerals are uraninite, uranothorianite, allanite, pyro-chlore and betafite in a gangue of smoky quartz with accessory zircon, molybdenite, amphibole and anatase. Minor calcite and fluorite are present. Unzoned pegmatites have UsOs contents of 0.024-0.117% in widths of l-4m." Reserves for Bicroft are unknown, but for the entire Bancroft area they are 2200 ton U3O8 at a grade of about 0.13%. 

QUARTZ, [CAS 14808-60-7]. The mineral quartz, oxide of the nonmctallic element silicon, is the commonest of minerals, and appears in a greater number of forms than any other. Its formula is SiC>2. Quartz commonly occurs in prismatic hexagonal crystals terminated by a pyramid. This pyramid is due to the equal development of two rhombohedrons, and may be observed in cases where one rhombohedron predominates. Cleavage is not observed the fracture is typically conchoidal, hardness is 7 specific gravity, 2.65 luster, vitreous to greasy or dull colorless to white, pink, purple, yellow, blue, green, smoky brown to nearly black transparent to opaque. 

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