Quartz

Hardness 7 on the Mohs scale, typically clear or white, vitreous luster, hexagonal crystal structure, no cleavage, specific gravity of 2.65

Forms in a wide variety of igneous, metamorphic, and sedimentary rocks. Often crystallizes from molten magma or precipitates from hot hydrothermal veins.

Used extensively in glassmaking, electronics (as an oscillator), abrasives, construction materials, and as a gemstone.

Quartz is the second most abundant mineral in Earth's continental crust, after feldspar. It exhibits piezoelectric properties, which is why it's used in watches and radios.

Identified by its hardness (scratches glass), lack of cleavage, and typical conchoidal fracture. Found worldwide in many geological environments.