mineral

Limonite-stained Quartz

Silicon Dioxide (SiO2) with Hydrated Iron Oxide (FeO(OH)·nH2O) coatings

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)

Hardness: 7 (Quartz) / 4-5
Luster: Vitreous to earthy

Identified June 13, 2026More mineral →

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Physical properties

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.

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Schist

Metamorphic

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

metamorphic

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Biotite Schist

Biotite-rich Schist [K(Mg,Fe)3AlSi3O10(F,OH)2]

metamorphic