metamorphic
Quartz-rich metamorphic rock, likely quartzite
Quartzite; predominantly crystalline SiO₂, with minor mica and iron-oxide impurities
AI-generated identification · may be incorrectTypically very hard (Mohs 7), gray to white with darker mica-rich patches, and a glassy to dull luster. Interlocking quartz grains give massive texture; cleavage is absent and fracture is irregular to conchoidal.
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Physical properties
Typically very hard (Mohs 7), gray to white with darker mica-rich patches, and a glassy to dull luster. Interlocking quartz grains give massive texture; cleavage is absent and fracture is irregular to conchoidal.
Formation & geological history
Formed when quartz-rich sandstone was recrystallized under elevated temperature and pressure during regional metamorphism. Its exact geological age cannot be determined from the photograph; ages vary widely by source terrane.
Uses & applications
Used as crushed stone, road aggregate, building stone, and decorative slabs; attractive pieces are collected but are generally not gemstone grade.
Geological facts
Quartzite commonly breaks through quartz grains rather than around them, unlike weakly cemented sandstone. Dark bands or patches may represent biotite, amphibole, graphite, or iron oxides.
Field identification & locations
Likely quartzite if it scratches glass and shows no loose grains; a streak test, acid test, and close inspection of grain boundaries would help distinguish it from quartz-bearing granite or veined metamorphic rock. Common in mountain belts and ancient metamorphic terrains.
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