metamorphic
Quartz-rich metamorphic rock, likely quartzite
Quartzite; predominantly SiO₂ with iron-oxide staining and minor feldspar/mica possible
AI-generated identification · may be incorrectHardness about 7 Mohs; gray, tan, and rusty orange, with a granular sugary texture and vitreous to dull luster. Quartz grains are interlocked and it lacks obvious cleavage; the orange coloration likely reflects hematite or limonite.
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Physical properties
Hardness about 7 Mohs; gray, tan, and rusty orange, with a granular sugary texture and vitreous to dull luster. Quartz grains are interlocked and it lacks obvious cleavage; the orange coloration likely reflects hematite or limonite.
Formation & geological history
Formed when quartz-rich sandstone was buried and recrystallized under heat and pressure, commonly during regional mountain-building; its exact geological age cannot be determined from the image. Weathering has oxidized iron-bearing impurities along fractures and grain boundaries.
Uses & applications
Used as crushed aggregate, road stone, building or decorative stone, and occasionally as a lapidary material. Attractive pieces may be polished, though this specimen appears ordinary and rough.
Geological facts
Quartzite is generally more resistant to weathering than the sandstone from which it formed, producing ridges and durable boulders. A useful test is that it scratches ordinary glass and breaks across grains rather than around them.
Field identification & locations
Common in metamorphic mountain belts worldwide, including the Appalachians, Rocky Mountains, Alps, and Precambrian shield regions. Confirm by testing hardness and checking for fused quartz grains; acid reaction would suggest carbonate contamination rather than pure quartzite.
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