metamorphic
Quartz-rich metamorphic rock, likely quartzite
Quartzite; predominantly crystalline SiO₂, possibly with mica or iron-oxide impurities
AI-generated identification · may be incorrectTypically very hard (Mohs 7), gray to white, with a sugary to glassy luster and interlocking quartz grains; it lacks obvious cleavage and breaks irregularly or conchoidally. The specimen’s metallic-looking surface may reflect mica, weathering, or a coating, so exact identification from the image is limited.
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Physical properties
Typically very hard (Mohs 7), gray to white, with a sugary to glassy luster and interlocking quartz grains; it lacks obvious cleavage and breaks irregularly or conchoidally. The specimen’s metallic-looking surface may reflect mica, weathering, or a coating, so exact identification from the image is limited.
Formation & geological history
Forms when quartz-rich sandstone is recrystallized under intense heat and pressure, commonly during regional mountain-building; ages vary from Precambrian to recent metamorphic belts. Common sources include mountain ranges and metamorphic terrains worldwide.
Uses & applications
Used as crushed stone, aggregate, road material, building stone, and occasionally countertops or decorative specimens; attractive varieties can be used for cabochons. This rough piece has modest commercial value.
Geological facts
Quartzite is generally harder and more resistant to weathering than its sandstone precursor. A useful test is that quartz grains cannot usually be scratched with a steel knife, though the surface should be tested inconspicuously.
Field identification & locations
Commonly found as resistant, angular to rounded float or ridges in metamorphic regions; look for fused quartz grains and no sandy texture. Likely locations include the Appalachians, Rocky Mountains, Brazil, India, and Scandinavia.
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