metamorphic
Quartz-rich metamorphic rock, likely quartzite
Quartzite; predominantly quartz (SiO₂), with minor mica and iron-oxide staining
AI-generated identification · may be incorrectHardness about 7 Mohs; white to gray and silvery, with vitreous to pearly luster. Granular, interlocking quartz crystals show little obvious cleavage; rusty brown areas are likely iron oxides, while dark flakes may be mica.
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Physical properties
Hardness about 7 Mohs; white to gray and silvery, with vitreous to pearly luster. Granular, interlocking quartz crystals show little obvious cleavage; rusty brown areas are likely iron oxides, while dark flakes may be mica.
Formation & geological history
Formed when quartz-rich sandstone was intensely metamorphosed, recrystallizing its grains into a fused quartz mosaic. Commonly Precambrian to Paleozoic, though quartzite forms in many mountain belts.
Uses & applications
Used as crushed stone, road aggregate, building stone, countertops, and decorative landscaping material; attractive pieces are collected but usually have modest value.
Geological facts
Unlike sandstone, true quartzite typically breaks across grains rather than around them. The specimen may alternatively be quartz-mica schist if the shiny minerals form a strong planar foliation.
Field identification & locations
Common in metamorphic mountain regions worldwide, including the Appalachians, Rocky Mountains, Alps, and Scandinavian mountains. Test with a steel file or glass: quartzite generally scratches glass and resists scratching; inspect for fused grains and any mica layering.
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