Is the mineral quartz composed solely of silica?

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Quartz Facts

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Quarts is a crystalline solid made of Silicon and Oxygen (SiO2). Quartz has a hardness of 7 on the Mohs scale. Quartz will scratch glass and has a white streak. Quarts will exhibit fracture - please do not mistake crystal faces for cleavage. Has many colours, often clear but may be white pink or brownish grey. Hexagonal Crystal system Piezoelectric properties. Moist common mineral in the earth's crust shows up as sand, flint, jasper, opal etc...