mineral

Ferruginous Quartz

SiO2 (Silicon Dioxide) with Iron Oxide inclusions (FeO(OH) / Fe2O3)

Hardness: 7 (Mohs scale); Color: White to tan with rusty brown, orange, or red staining; Luster: Vitreous to dull (earthy where stained); Crystal Structure: Hexagonal; Cleavage: None/Conchoidal fracture; Specific Gravity: 2.65.

Hardness: 7 (Mohs scale)
Color: White to tan with rusty brown, orange, or red staining
Luster: Vitreous to dull (earthy where stained)

Identified March 26, 2026More mineral →

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Physical properties

Formation & geological history

Formed through hydrothermal processes where silica-rich fluids crystallize in veins or pockets. The distinctive color comes from secondary oxidation of iron-bearing minerals or groundwater staining infiltrating the quartz matrix.

Uses & applications

Used primarily as low-grade decorative stone, landscape aggregate, or as a source of high-purity silica in industrial glassmaking if refined; frequently collected as garden rocks or by amateur geologists.

Geological facts

Also known as 'Iron-stained Quartz' or 'Limonitic Quartz.' The presence of the deep rust color often indicates that the quartz formed in an environment rich in iron-bearing sulfides like pyrite, which have since weathered away.

Field identification & locations

Identify in the field by its high hardness (cannot be scratched by a steel knife) and greasy-to-glassy luster when freshly broken. Commonly found in quartz veins, road cuts, and mountain scree globally. Collectors should look for internal clarity or unique banding.

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