metamorphic
Quartz-rich metamorphic rock, likely quartzite
Quartzite; predominantly microcrystalline quartz (SiO₂), possibly with feldspar, mica, or iron-oxide staining
AI-generated identification · may be incorrectHardness about 7 Mohs; pale gray to white with tan-brown weathering, sugary granular texture, and vitreous to dull luster. Quartz grains appear tightly interlocked, with no obvious cleavage and irregular fracture; density is typically 2.6–2.7 g/cm³.
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Physical properties
Hardness about 7 Mohs; pale gray to white with tan-brown weathering, sugary granular texture, and vitreous to dull luster. Quartz grains appear tightly interlocked, with no obvious cleavage and irregular fracture; density is typically 2.6–2.7 g/cm³.
Formation & geological history
Formed when quartz-rich sandstone was subjected to heat and pressure, recrystallizing its grains; commonly Precambrian to Paleozoic, though age depends on the source formation. It commonly occurs in metamorphic belts and resistant ridges.
Uses & applications
Used as crushed stone, aggregate, dimension stone, road material, and silica feedstock; attractive pieces may be collected, but this specimen has limited gem or decorative value.
Geological facts
Quartzite is generally harder and more resistant to weathering than the sandstone from which it formed. A strong acid reaction would indicate carbonate contamination rather than pure quartzite.
Field identification & locations
Common in mountain belts worldwide, including the Appalachian Mountains, Rocky Mountains, Alps, and many Precambrian shields. A steel file should have little effect, while quartz-rich surfaces commonly scratch glass; value is usually $2–$15 for an ordinary hand specimen.
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