metamorphic
Iron-rich quartzite or iron-stained quartz
Quartzite; predominantly quartz (SiO₂) with iron-oxide/hydroxide coatings, possibly minor mica or feldspar
AI-generated identification · may be incorrectHardness about 7 Mohs; granular, gray-white to rusty yellow-brown, with a vitreous to dull luster and no obvious cleavage. The sparkling grains and brown coloration suggest quartz crystals cemented or recrystallized with iron oxides.
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Physical properties
Hardness about 7 Mohs; granular, gray-white to rusty yellow-brown, with a vitreous to dull luster and no obvious cleavage. The sparkling grains and brown coloration suggest quartz crystals cemented or recrystallized with iron oxides.
Formation & geological history
Likely formed when quartz-rich sandstone was metamorphosed and recrystallized, with later weathering depositing limonite/goethite; age cannot be determined from the photograph. It commonly occurs in metamorphic belts and iron-rich weathering zones.
Uses & applications
Used as crushed stone, aggregate, building stone, and occasionally as a decorative or lapidary material; this small piece has little commercial value.
Geological facts
Iron staining can produce vivid yellow, orange, and brown colors without making quartz itself yellow. A glass-scratch test can help confirm quartz, though it may damage the specimen.
Field identification & locations
Common in quartzite outcrops, stream gravels, and weathered rock piles. Look for very hard granular texture, fused quartz grains, and rusty coatings; a definitive identification would require testing and possibly microscopy.
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