igneous
Quartz-bearing granite or granitic pegmatite
Crystalline quartz (SiO₂) with feldspar and dark mica/amphibole; likely weathered granite
AI-generated identification · may be incorrectHardness about 6–7 Mohs; pale cream to white, with translucent quartz and darker gray-green minerals. Typically a coarse crystalline texture, vitreous quartz luster, irregular fracture, and weak feldspar cleavage; the specimen appears weathered and iron-stained.
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Physical properties
Hardness about 6–7 Mohs; pale cream to white, with translucent quartz and darker gray-green minerals. Typically a coarse crystalline texture, vitreous quartz luster, irregular fracture, and weak feldspar cleavage; the specimen appears weathered and iron-stained.
Formation & geological history
Formed when silica-rich magma slowly cooled underground, allowing large interlocking crystals to grow; commonly Precambrian to Phanerozoic in age depending on locality. Surface weathering produced the yellow-brown staining and softened outer areas.
Uses & applications
Used as crushed stone, aggregate, dimension stone, and occasionally as a decorative lapidary material. This rough piece has little jewelry value unless it contains unusually large, clear quartz crystals.
Geological facts
The pale massive portion is probably quartz-rich material, while the dark matrix is granite or a related metamorphosed granitic rock. Quartz resists weathering, often remaining as prominent knobs or veins after surrounding minerals decompose.
Field identification & locations
Look for visible interlocking quartz and feldspar grains, lack of layering, and a scratch resistance near glass; a steel nail will not scratch quartz. Common in continental crust, granite outcrops, pegmatites, and quartz veins worldwide.
