metamorphic
Weathered quartz-rich metamorphic rock, likely quartzite
Quartzite (mostly SiO₂), possibly micaceous quartzite or quartz-rich schist
AI-generated identification · may be incorrectTypically very hard (Mohs 7), granular and glassy to sugary luster, with quartz grains and possible mica flakes; the specimen appears brown-orange from iron-oxide weathering. Massive quartzite lacks cleavage, while mica-rich varieties show weak foliation; specific gravity is about 2.6–2.7.
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Physical properties
Typically very hard (Mohs 7), granular and glassy to sugary luster, with quartz grains and possible mica flakes; the specimen appears brown-orange from iron-oxide weathering. Massive quartzite lacks cleavage, while mica-rich varieties show weak foliation; specific gravity is about 2.6–2.7.
Formation & geological history
Forms when quartz-rich sandstone is recrystallized during regional metamorphism, commonly during mountain-building; its exact geological age cannot be determined from the image. Iron-bearing groundwater commonly produces the rusty surface staining.
Uses & applications
Used as crushed stone, road aggregate, landscaping stone, and durable building or countertop material; attractive pieces may be collected but are generally low-value.
Geological facts
Quartzite is commonly more resistant to weathering than surrounding rocks, producing ridges and prominent boulders. It can resemble chert or weathered granite, but typically breaks across interlocking quartz grains rather than around sand grains.
Field identification & locations
Look for a gritty, fused quartz texture, high hardness, and inability to scratch quartz or glass easily; a steel nail should not scratch it. Common worldwide in metamorphic belts, including the Appalachians, Rocky Mountains, India, Brazil, and Scandinavia.
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