metamorphic
Quartzite (probable)
Quartzite; predominantly recrystallized quartz (SiO₂)
AI-generated identification · may be incorrectHardness about 7 Mohs; pale tan, gray, and rusty brown; vitreous to sugary luster; interlocking quartz grains with no obvious cleavage. The surface appears weathered and iron-stained, though the image does not show diagnostic grain detail clearly.
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Physical properties
Hardness about 7 Mohs; pale tan, gray, and rusty brown; vitreous to sugary luster; interlocking quartz grains with no obvious cleavage. The surface appears weathered and iron-stained, though the image does not show diagnostic grain detail clearly.
Formation & geological history
Formed when quartz-rich sandstone was subjected to heat and pressure, causing recrystallization. Typically Precambrian to Paleozoic or younger, depending on the source terrain; quartzite is plausible in the metamorphic belts and glacially transported deposits of northeastern Washington.
Uses & applications
Used as durable building stone, aggregate, road material, and ornamental or landscape rock; attractive pieces may be collected, but this specimen appears common and unpolished.
Geological facts
Quartzite commonly breaks across grains rather than around them, producing sharp, irregular fractures. A steel file should generally fail to scratch fresh quartzite, while quartz-rich sandstone may crumble or show visible cement between grains.
Field identification & locations
Likely identification: weathered quartzite or strongly silicified sandstone. Look for a uniformly hard, fused texture and abundant sparkling quartz; acid testing is usually negative. Common regional alternatives include quartz-rich metamorphic rock, vein quartz, or silicified volcanic rock.
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