metamorphic
Quartz-rich metamorphic rock, likely quartzite
Quartzite; predominantly crystalline SiO₂, possibly with mica or feldspar
AI-generated identification · may be incorrectHardness about 7 Mohs; gray to tan, with a granular sugary texture and dull to glassy luster. Quartzite generally lacks cleavage and breaks irregularly or conchoidally, with specific gravity around 2.6–2.7.
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Physical properties
Hardness about 7 Mohs; gray to tan, with a granular sugary texture and dull to glassy luster. Quartzite generally lacks cleavage and breaks irregularly or conchoidally, with specific gravity around 2.6–2.7.
Formation & geological history
Formed when quartz-rich sandstone was intensely buried and recrystallized during metamorphism, commonly during Precambrian to Paleozoic mountain-building events. The image suggests a foliated or layered variety, so mica-rich metasedimentary rock is also possible.
Uses & applications
Used as crushed stone, aggregate, landscaping stone, building slabs, and occasionally decorative material; attractive specimens may be collected but are usually low-value.
Geological facts
Quartzite is commonly confused with sandstone; unlike sandstone, it fractures across individual grains rather than crumbling around them. Visible layering may indicate mica-rich quartzite or metasandstone.
Field identification & locations
Test with a steel file or knife: true quartzite resists scratching, while calcite-rich rocks do not; dilute hydrochloric acid should cause little or no fizzing. Common in metamorphic mountain belts worldwide, including India, Brazil, the United States, and Scandinavia.
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