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Quartz is, therefore, classified structurally as a framework silicate mineral and compositionally as an oxide mineral. Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar. [10] Quartz exists in two forms, the normal α-quartz and the high-temperature β-quartz, both of which are chiral. The transformation ...
Crystals show pleochroism from red to blue to violet. Dumortierite quartz is blue colored quartz containing abundant dumortierite inclusions. Dumortierite was first described in 1881 for an occurrence in Chaponost , in the Rhône - Alps of France and named for the French paleontologist Eugène Dumortier (1803–1873). [ 5 ]
Turquoise is an opaque, blue-to-green mineral that is a hydrous phosphate of copper and aluminium, with the chemical formula Cu Al 6 (PO 4) 4 8 ·4H 2 O.It is rare and valuable in finer grades and has been prized as a gemstone for millennia due to its hue.
Epidosite – Hydrothermally altered epidote- and quartz-bearing rock; Felsite – Very fine-grained volcanic rock that sometimes contains larger crystals; Flint – Cryptocrystalline form of the mineral quartz; Ganister – Hard, fine-grained quartzose sandstone, or orthoquartzite; Gossan – Intensely oxidized, weathered or decomposed rock
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.
Llanite is a porphyritic rhyolite with distinctive phenocrysts of blue quartz (a rare quartz color) and perthitic feldspar (light grayish-orangeish). The brown, fine-grained groundmass consists of very small quartz, feldspar, and biotite mica crystals.
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Flint, occasionally flintstone, is a sedimentary cryptocrystalline form of the mineral quartz, [1] [2] categorized as the variety of chert that occurs in chalk or marly limestone. Historically, flint was widely used to make stone tools and start fires. Flint occurs chiefly as nodules and masses in sedimentary rocks, such as chalks and limestones.