metamorphic
Quartz-rich rock, likely milky quartz or quartzite
Quartz (SiO₂); possibly quartzite, a recrystallized quartz sandstone
AI-generated identification · may be incorrectPale gray-white, dull to weakly glassy luster, massive and fine-grained with no obvious cleavage; quartz hardness is 7 Mohs, and specific gravity is about 2.65. The irregular, weathered surface and granular texture favor quartzite over a single crystal.
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Physical properties
Pale gray-white, dull to weakly glassy luster, massive and fine-grained with no obvious cleavage; quartz hardness is 7 Mohs, and specific gravity is about 2.65. The irregular, weathered surface and granular texture favor quartzite over a single crystal.
Formation & geological history
Quartzite forms when quartz sandstone is metamorphosed under heat and pressure, commonly during mountain building; its age depends on the source formation and cannot be determined from the image. If it is milky quartz, it instead formed from silica-rich hydrothermal fluids filling fractures.
Uses & applications
Common quartzite is used as aggregate, roadstone, building stone, and occasionally countertops; attractive quartz specimens are collected but this small weathered piece has minimal commercial value.
Geological facts
Quartz is one of Earth’s most abundant minerals and has conchoidal fracture rather than cleavage. Quartzite typically resists weathering and leaves a white streak, while quartz may show translucent edges.
Field identification & locations
Common in metamorphic terrains, mountain belts, stream gravels, and hydrothermal veins worldwide. Test with a steel file or glass: it should scratch glass; a vinegar test is generally uninformative.
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