mineral

Rock crystal (clear quartz)

Quartz, silicon dioxide (SiO₂)

AI-generated identification · may be incorrect

Hardness 7 Mohs; colorless to milky-white, transparent to translucent, with vitreous luster and a hexagonal crystal structure. Quartz has no true cleavage and commonly shows conchoidal fracture; the pictured pieces appear rough or broken rather than well-crystallized.

Identified September 7, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich fluids or melts cool, commonly in hydrothermal veins, cavities, and igneous rocks. Quartz is abundant from Precambrian to modern ages, so age cannot be determined from the image.

Uses & applications

Used in glass, ceramics, electronics, abrasives, engineered stone, and watches; clear, well-formed crystals are collected and occasionally cut as gemstones.

Geological facts

Quartz is one of Earth’s most abundant minerals and is piezoelectric, producing an electrical charge when stressed.

Field identification & locations

Identify by its glassy appearance, conchoidal fracture, lack of cleavage, and ability to scratch ordinary glass; unlike calcite, it does not readily fizz in dilute acid. Common worldwide, especially in Brazil, Madagascar, Arkansas, and alpine-type veins.