metamorphic
Weathered quartz-rich metamorphic rock, likely quartzite
Quartzite (mostly microcrystalline quartz, SiO₂), possibly altered sandstone
AI-generated identification · may be incorrectPale gray-white, granular and dull to weakly vitreous; massive with no obvious cleavage. Quartzite has Mohs hardness about 7 and specific gravity near 2.6; the rough, weathered surface obscures individual grains and minor dark impurities.
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Physical properties
Pale gray-white, granular and dull to weakly vitreous; massive with no obvious cleavage. Quartzite has Mohs hardness about 7 and specific gravity near 2.6; the rough, weathered surface obscures individual grains and minor dark impurities.
Formation & geological history
Forms when quartz-rich sandstone is recrystallized under metamorphic heat and pressure, commonly during mountain-building. The image cannot establish geological age; quartzite is regionally plausible near Spokane, Washington, where metamorphic and sedimentary rocks occur.
Uses & applications
Useful as durable crushed stone, aggregate, paving and decorative stone; attractive pieces may be used as lapidary material, though this specimen appears ordinary and unpolished.
Geological facts
Its key diagnostic property is that broken grains commonly fracture through the quartz grains rather than separating along bedding. A steel nail should not scratch it; quartz may scratch glass.
Field identification & locations
Look for a sugary quartz texture, very high hardness, and little or no fizz with dilute hydrochloric acid. If it fizzes strongly, it is more likely limestone or marble; if grains remain visibly sandy and it scratches less readily, sandstone is a better identification.
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