metamorphic
Blue-gray quartz-rich rock, likely quartzite
Quartzite; predominantly microcrystalline quartz (SiO₂), possibly with mica or feldspar
AI-generated identification · may be incorrectTypically Mohs hardness 7, pale blue-gray color, vitreous to dull luster, granular crystalline texture, and no obvious cleavage; the visible bluish coloration may reflect inclusions or surface treatment. Exact identification is limited by the single photograph.
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Physical properties
Typically Mohs hardness 7, pale blue-gray color, vitreous to dull luster, granular crystalline texture, and no obvious cleavage; the visible bluish coloration may reflect inclusions or surface treatment. Exact identification is limited by the single photograph.
Formation & geological history
Formed when quartz-rich sandstone recrystallized under heat and pressure during metamorphism; ages vary widely by locality, commonly Precambrian to Paleozoic. It commonly occurs in metamorphic mountain belts.
Uses & applications
Used as crushed stone, aggregate, paving, and building or decorative stone; attractive pieces may be collected or polished, though this specimen appears rough and ordinary.
Geological facts
Quartzite commonly breaks across grains rather than around them and is harder than glass. Blue-gray varieties can be confused with slate, chert, or quartz-bearing gneiss.
Field identification & locations
Look for grains fused into a hard, sugary mass; it should scratch ordinary glass, while a steel nail generally will not scratch it. Common worldwide, including Brazil, India, the United States, and Norway.
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