metamorphic
Likely quartzite
Quartzite, composed predominantly of quartz (SiO₂)
AI-generated identification · may be incorrectGray-blue, dull to slightly vitreous surface; quartz has Mohs hardness 7 and a trigonal crystal structure, but individual grains and cleavage are not clear in this photo. The specimen appears massive and fractured, so identification is provisional.
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Physical properties
Gray-blue, dull to slightly vitreous surface; quartz has Mohs hardness 7 and a trigonal crystal structure, but individual grains and cleavage are not clear in this photo. The specimen appears massive and fractured, so identification is provisional.
Formation & geological history
Forms when quartz-rich sandstone is recrystallized under heat and pressure during metamorphism; formation age depends on its source and cannot be determined from appearance alone.
Uses & applications
Quartzite is used as crushed stone and building material; attractive pieces may be kept as display or teaching specimens.
Geological facts
True quartzite is very hard and typically breaks through quartz grains rather than around them.
Field identification & locations
Look for a dense, hard rock with interlocking quartz grains; it commonly occurs in metamorphic belts worldwide. A scratch test and examination of a fresh surface would help distinguish it from other gray rocks.
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