mineral
Limonite-stained Quartz
Silicon Dioxide (SiO2) with Hydrated Iron Oxide (FeO(OH)·nH2O) coatings
AI-generated identification · may be incorrectHardness: 7 (Quartz) / 4-5.5 (Limonite coating); Color: Dirty white to light tan with yellow-brown or reddish staining; Luster: Vitreous to earthy; Crystal Structure: Hexagonal; Cleavage: None/Conchoidal fracture; Specific gravity: 2.6-2.7 (Quartz portion)
- Hardness
- 7 (Quartz) / 4-5
- Luster
- Vitreous to earthy
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Physical properties
Hardness: 7 (Quartz) / 4-5.5 (Limonite coating); Color: Dirty white to light tan with yellow-brown or reddish staining; Luster: Vitreous to earthy; Crystal Structure: Hexagonal; Cleavage: None/Conchoidal fracture; Specific gravity: 2.6-2.7 (Quartz portion)
Formation & geological history
Formed via hydrothermal processes where quartz crystallized in veins, later subjected to chemical weathering and oxidation where iron-bearing fluids deposited a limonite crust or stain. These are found in oxygen-rich surface environments across all geological ages.
Uses & applications
Primarily of interest to collectors or as indicator minerals for prospectors looking for mineralized veins; raw quartz is used in electronics and glass-making, while limonite was historically used as an ochre pigment.
Geological facts
The yellow-brown 'staining' is actually rust (hydrated iron oxides). In gold-bearing regions, this 'rusty quartz' or 'gossan' appearance is often a primary target for prospectors as it indicates the oxidation of sulfide minerals that may have contained gold.
Field identification & locations
Identify by its high hardness (will scratch glass) paired with the distinct yellowish-brown earthy coating that cannot be washed off easily. Commonly found in eroded creek beds or outcrops near hydrothermal vein systems.
