mineral

Milky quartz (rough quartz specimen)

Quartz, silicon dioxide (SiO₂)

AI-generated identification · may be incorrect

White to translucent, glassy-to-waxy luster with irregular crystalline surfaces; Mohs hardness 7, no cleavage, conchoidal fracture, and hexagonal crystal structure. The brownish patches may be iron-oxide staining or attached matrix.

Identified August 21, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich fluids crystallize in veins, cavities, and pegmatites, commonly during igneous or metamorphic activity. Quartz is geologically widespread and may form across much of Earth’s history.

Uses & applications

Common quartz is used in glass, ceramics, abrasives, electronics, and engineered stone; attractive pieces are sold as inexpensive mineral specimens. Typical value is about $3–$25, or up to $50+ if unusually clear, crystalline, or aesthetically distinctive.

Geological facts

Quartz is one of Earth’s most abundant minerals and is chemically resistant to weathering. Its lack of cleavage and hardness make it useful for recognizing it against softer white minerals such as calcite.

Field identification & locations

Common in hydrothermal veins, granite-related pegmatites, metamorphic rocks, and river gravels worldwide, including Brazil, Madagascar, the United States, and many other regions. A steel nail should not scratch it; glass is typically scratched by quartz, while dilute acid does not visibly fizz.