mineral
Quartz-rich iron-stained nodule
Microcrystalline quartz (SiO₂), possibly chalcedony with limonite/goethite staining
AI-generated identification · may be incorrectGray, rounded, waxy to dull luster with a granular pale-gold iron-oxide patch; likely hardness about 6.5–7 Mohs, no obvious cleavage, conchoidal fracture, and specific gravity near 2.6. The surface appears naturally weathered or lightly polished.
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Physical properties
Gray, rounded, waxy to dull luster with a granular pale-gold iron-oxide patch; likely hardness about 6.5–7 Mohs, no obvious cleavage, conchoidal fracture, and specific gravity near 2.6. The surface appears naturally weathered or lightly polished.
Formation & geological history
Probably formed as silica-rich groundwater filled a cavity or replaced host rock, later acquiring brown-yellow limonite/goethite staining from oxidation. Exact age and locality cannot be determined from the photograph; such nodules occur in sedimentary and volcanic terrains.
Uses & applications
Primarily a collecting specimen; quartz/chalcedony is used in abrasives, glass, electronics, and ornamental stone, while iron oxides provide pigment. The pictured piece has little commercial value unless its locality or internal pattern is notable.
Geological facts
The metallic-looking golden area is more likely iron oxide or mica than native gold. A steel file should barely scratch quartz, while quartz will scratch ordinary glass.
Field identification & locations
Commonly found as rounded nodules in weathered volcanic rocks, limestone, gravels, and silica-rich veins. Confirm with a hardness test, streak test, magnification, and—if valuable—specific-gravity or elemental analysis.
