silicatesquartz

Silicatesquartz, usually referred to simply as quartz, is a mineral and the most common form of silica, with the chemical formula SiO2. It is a tectosilicate that forms a three-dimensional framework of silicon-oxygen tetrahedra (SiO4) linked through shared oxygen atoms. Quartz crystallizes in the hexagonal crystal system and commonly occurs as prismatic crystals with six-sided terminations, though it is also found in massive or granular forms.

Quartz exhibits a hardness of 7 on the Mohs scale and a specific gravity around 2.65. It shows conchoidal fracture and has no true cleavage. Color is typically colorless or white, but impurities can produce a wide range of colors, including amethyst (purple), citrine (yellow-orange), rose quartz, and smoky quartz. The mineral occurs in many environments and can be free-standing crystals or intergrown with other silicates.

Alpha-quartz is the stable form at room temperature and below about 573°C (under ambient pressure); above that temperature, beta-quartz forms, a reversible phase transition with different symmetry. Quartz is highly resistant to chemical weathering and is abundant in igneous rocks such as granites and rhyolites, in metamorphic rocks like schists and gneisses, and in sedimentary deposits derived from silica-rich fluids. It also forms in hydrothermal veins and pegmatites. Microcrystalline varieties include chalcedony, agate, and jasper, while macrocrystalline varieties include clear quartz and colored varieties used as gemstones.

Uses of quartz are diverse. It is essential in electronics and timekeeping, where quartz crystals provide precise oscillators. Industrially, quartz is used in glassmaking, ceramics, and as an abrasive, and high-purity quartz serves as a source of silicon for semiconductors. Exposure to quartz dust can pose health risks such as silicosis, making proper handling important in mining and processing.

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