Quartz

Hardness of 7 on the Mohs scale, vitreous luster, conchoidal fracture, and hexagonal crystal system. Specific gravity is 2.65.

Forms in igneous, metamorphic, and sedimentary environments from cooling silica-rich fluids or magma.

Used in electronics, glassmaking, abrasive powders, and ornamental jewelry or crystal collecting.

Quartz is the second most abundant mineral in Earth's continental crust. It exhibits piezoelectric properties, making it useful in watches and electronics.

Identified by its high hardness (scratches glass), lack of cleavage, and distinct conchoidal fracture. Found globally, including pegmatites and hydrothermal veins.