quartz

n. silicon dioxide, most abundant mineral

Quartz (from German ) is the second most common mineral in the Earth's continental crust, feldspar being the first. It is made up of a lattice of silica (O) tetrahedra. Quartz has a hardness of 7 on the Mohs scale and a density of 2.65 g/cm³.
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Noun
1. colorless glass made of almost pure silica
(synonym) quartz glass, vitreous silica, lechatelierite, crystal
(hypernym) natural glass
2. a hard glossy mineral consisting of silicon dioxide in crystal form; present in most rocks (especially sandstone and granite); yellow sand is quartz with iron oxide impurities
(hypernym) mineral
(hyponym) quartz crystal
(substance-meronym) silicon, Si, atomic number 14

n. quartz, silicon dioxide, most abundant mineral

(n.)
A form of silica, or silicon dioxide (SiO2), occurring in hexagonal crystals, which are commonly colorless and transparent, but sometimes also yellow, brown, purple, green, and of other colors; also in cryptocrystalline massive forms varying in color and degree of transparency, being sometimes opaque.