mineral

Milky quartz with iron-oxide staining

Quartz, silicon dioxide (SiO₂), commonly with hematite/goethite inclusions

AI-generated identification · may be incorrect

White to cream, opaque, massive quartz with a vitreous-to-dull luster and irregular fracture; hardness 7 Mohs, no cleavage, specific gravity about 2.65. Gray-brown patches are likely iron oxides or included host material; crystal faces are not evident.

Identified September 4, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich hydrothermal fluids fill fractures or cavities, or during pegmatitic growth; quartz is geologically widespread from Precambrian to modern environments. The specimen may be a vein fragment rather than a complete crystal.

Uses & applications

Quartz is used in glass, ceramics, abrasives, electronics, and engineered stone; attractive pieces are collected or used decoratively. This rough, heavily stained specimen has limited gem value.

Geological facts

Quartz is one of Earth’s most abundant minerals and is piezoelectric. A steel file should not scratch it, while quartz can scratch ordinary glass.

Field identification & locations

Common in hydrothermal veins, pegmatites, metamorphic rocks, and quartz-rich gravels worldwide, especially Brazil, Madagascar, the United States, and Europe. Confirm with hardness, glass-scratching ability, and lack of cleavage; acid testing is unnecessary.