Mineral

Milky Quartz with Iron Staining

Quartz (Silicon Dioxide - SiO2)

Hardness: 7 on Mohs scale; Color: Milky white to opaque tan/brown due to iron oxide impurities; Luster: Vitreous to greasy; Crystal Structure: Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Milky white to opaque tan/brown due to iron oxide impurities
Luster: Vitreous to greasy

Identified March 6, 2026More mineral →

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Physical properties

Formation & geological history

Formed in hydrothermal veins or as a constituent in igneous pegmatites. This specimen likely weathered out of a vein and spent time in a riverbed or soil environment where iron-rich waters stained the surface. It can date from the Precambrian to present depending on the local tectonic environment.

Uses & applications

Used industrially as a source of silica for glassmaking, abrasives, and electronics. Common varieties are used for landscaping, road base, and as decorative pocket stones for collectors.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. The 'milky' appearance is caused by tiny inclusions of gas or liquid trapped during crystal growth. Iron staining (appearing as orange/brown rust) is a common surface feature when quartz is exposed to groundwater.

Field identification & locations

Identify in the field by its inability to be scratched by a steel knife (H=7) and its lack of cleavage. It is found globally in almost all geological environments, particularly in mountainous regions and river gravels. Collectors should look for unique crystal terminations or inclusions.

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