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Chalcedony's standard chemical structure (based on the chemical structure of quartz) is SiO 2 (silicon dioxide). Chalcedony has a waxy luster, and may be semitransparent or translucent. It can assume a wide range of colors, but those most commonly seen are white to gray, grayish-blue or a shade of brown ranging from pale to nearly black.
Generally, dark navy blue chrysocolla is too soft to be used in jewelry, while cyan, green, and blue-green chrysocolla can have a hardness approaching 6, similar to turquoise. Chrysocolla chalcedony is a heavily silicified form of chrysocolla that forms in quartz deposits and can be very hard and approach a hardness of 7. [9] [10] [11]
Blue lace agate is a pale blue and white lace agate found primarily in Namibia. These agates formed in dolomite associated with igneous rock. Botswana agates are found in basaltic rocks of the Permian age in Botswana. They feature contrasting bands of purple, pink, black, grey, and white.
Pietersite is a commercial term for a variety of the mineral chalcedony. Originating from Namibia and China, where it is mined for use as a decorative stone due to its chaotic chatoyancy and brecciated structure. Ranging in colour from brownish-red, to blue-grey, and chatoyant yellow.
Other colors of chalcedony may also occur in Indian bloodstone, such as white, yellow, or blue. This semiprecious stone should not be confused with other ornamental stones that contain red jasper. Setonite, also called African bloodstone, is composed of red jasper, grey chalcedony, and pyrite .
Jasper, an aggregate of microgranular quartz and/or cryptocrystalline chalcedony and other mineral phases, [1] [2] is an opaque, [3] impure variety of silica, usually red, yellow, brown or green in color; and rarely blue. The common red color is due to iron(III) inclusions.
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Chrysoprase, chrysophrase or chrysoprasus is a gemstone variety of chalcedony (a cryptocrystalline form of silica) that contains small quantities of nickel.Its color is normally apple-green, but varies from turquoise-like cyan to deep green.