metamorphic
Quartz-rich metamorphic rock, likely quartzite
Quartzite; predominantly crystalline quartz (SiO₂), possibly with mica and feldspar
AI-generated identification · may be incorrectWhite to gray, coarse granular texture with glassy to pearly luster; quartz hardness is 7 Mohs, no cleavage, conchoidal fracture, and specific gravity about 2.65. The specimen appears strongly recrystallized and may contain minor mica or feldspar.
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Physical properties
White to gray, coarse granular texture with glassy to pearly luster; quartz hardness is 7 Mohs, no cleavage, conchoidal fracture, and specific gravity about 2.65. The specimen appears strongly recrystallized and may contain minor mica or feldspar.
Formation & geological history
Forms when quartz-rich sandstone is recrystallized under heat and pressure during regional metamorphism, commonly during mountain-building; its exact geological age cannot be determined from the photograph.
Uses & applications
Used as durable crushed stone, building and paving material, and decorative stone; attractive pieces are collected but are generally not gemstones.
Geological facts
Quartzite is harder and more resistant to weathering than its sandstone precursor. A true quartzite typically breaks through quartz grains rather than around them.
Field identification & locations
Common in metamorphic mountain belts worldwide, including the Appalachians, Rockies, Alps, and Scandinavian mountains. Test with a steel nail or glass only cautiously: quartzite should scratch glass and resist a steel knife; acid produces no reaction.
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