metamorphic
Quartz-bearing metamorphic rock, likely quartzite
Quartzite, predominantly SiO₂, with possible feldspar and mica impurities
AI-generated identification · may be incorrectHardness about 7 Mohs; gray, white, and rusty-brown coloration with a granular, sugary texture and vitreous to dull luster. Quartz grains appear interlocked; cleavage is absent or poor, and specific gravity is approximately 2.65.
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Physical properties
Hardness about 7 Mohs; gray, white, and rusty-brown coloration with a granular, sugary texture and vitreous to dull luster. Quartz grains appear interlocked; cleavage is absent or poor, and specific gravity is approximately 2.65.
Formation & geological history
Formed when quartz-rich sandstone was intensely heated and compressed during metamorphism, welding the grains together; specimens may range from Precambrian to younger mountain-building events. The image alone cannot establish its precise age or locality.
Uses & applications
Used as crushed stone, aggregate, paving, and durable building stone; attractive pieces may be collected or polished, though this specimen appears ordinary and unpolished.
Geological facts
Quartzite commonly breaks across grains rather than around them, making it tougher than sandstone. Brown areas may reflect iron-oxide staining, while the darker portion could contain mica or other metamorphic minerals.
Field identification & locations
Look for a very hard, grainy rock that scratches glass and does not fizz with dilute acid; sandstone typically feels less cohesive and breaks around grains. Common in metamorphic mountain belts worldwide, including the Appalachian Mountains, Alps, and Himalayas.
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