mineral

Milky quartz with iron-oxide staining

Quartz, silicon dioxide (SiO₂)

AI-generated identification · may be incorrect

Hardness 7 Mohs; translucent white to gray with rusty yellow-brown inclusions, vitreous luster, no cleavage, and irregular conchoidal fracture. Quartz is trigonal, though this specimen appears massive rather than well-crystallized.

Identified August 30, 2026More mineral →

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Physical properties

Formation & geological history

Formed when silica-rich fluids deposited quartz in fractures or cavities, later acquiring iron-oxide staining. Quartz veins occur from ancient Precambrian rocks to relatively young hydrothermal systems.

Uses & applications

Used in glass, ceramics, electronics, abrasives, and engineered stone; attractive pieces are sold as inexpensive mineral specimens. Typical value is about $2–$15, occasionally $20–$50 if crystals or inclusions are especially attractive.

Geological facts

The brown coloration is likely limonite/goethite rather than part of the quartz itself. Quartz scratches ordinary glass and is substantially harder than most tile surfaces.

Field identification & locations

Common worldwide in hydrothermal veins, pegmatites, and metamorphic rocks, including Brazil, Madagascar, the United States, and Europe. Confirm with a glass-scratch test and inspect for quartz’s curved fracture; avoid testing on valuable polished surfaces.