metamorphic
Quartz-rich metamorphic rock, likely quartzite
Quartzite; predominantly quartz (SiO₂) with iron-oxide staining and minor feldspar/mica
AI-generated identification · may be incorrectHardness about 7 Mohs; white to gray and reddish-brown, with a vitreous to dull luster and massive, interlocking quartz grains. It lacks obvious cleavage and has a specific gravity near 2.6–2.7; the brown-red colors are likely hematite or limonite.
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Physical properties
Hardness about 7 Mohs; white to gray and reddish-brown, with a vitreous to dull luster and massive, interlocking quartz grains. It lacks obvious cleavage and has a specific gravity near 2.6–2.7; the brown-red colors are likely hematite or limonite.
Formation & geological history
Forms when quartz-rich sandstone is recrystallized under heat and pressure during regional metamorphism, commonly during mountain-building; its exact age cannot be determined from the photograph. It commonly occurs in metamorphic belts and resistant ridges.
Uses & applications
Used as crushed stone, aggregate, landscaping rock, and durable building or decorative stone; attractive polished pieces are collected but usually have modest value.
Geological facts
Quartzite commonly breaks across grains rather than around them, unlike sandstone, and can scratch ordinary glass. Iron-rich fluids may produce the irregular red-brown veining visible here.
Field identification & locations
Likely quartzite if a fresh edge shows fused, sugary quartz grains and the specimen scratches glass; dilute acid should not fizz unless carbonate minerals are present. Common localities include the Appalachian Mountains, Rocky Mountains, India, Brazil, and Scandinavia.
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