mineral

Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Colorless (clear); Luster: Vitreous (glassy); Crystal structure: Hexagonal (trigonal); Cleavage: Indistinct/Conchoidal fracture; Specific Gravity: 2.65.

Hardness: 7 on Mohs scale
Color: Colorless (clear)
Luster: Vitreous (glassy)

Identified May 24, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: Colorless (clear); Luster: Vitreous (glassy); Crystal structure: Hexagonal (trigonal); Cleavage: Indistinct/Conchoidal fracture; Specific Gravity: 2.65.

Formation & geological history

Forms in a wide variety of environments including cooling magma (igneous), hydrothermal veins, and metamorphic rocks. It is one of the most abundant minerals in the Earth cortex and can form at almost any geological age.

Uses & applications

Used in electronics (oscillators), glassmaking, abrasives, jewelry (semi-precious gemstone), and as a popular specimen for collectors.

Geological facts

Quartz is piezoelectric, meaning it generates an electric charge in response to applied mechanical stress. Clear quartz is often called 'Rock Crystal' and was once believed by ancient Greeks to be permanently frozen ice.

Field identification & locations

Identify in the field by its hardness (will scratch glass), glassy luster, and lack of true cleavage. It is found globally in mountains, riverbeds, and sandy beaches.