metamorphic
Polished/tumbled light-colored stone, possibly quartzite or marble
Uncertain; likely quartzite (mostly SiO₂) or calcite marble (CaCO₃)
AI-generated identification · may be incorrectSmooth, rounded, pale gray-white, and fine-grained with a dull-to-satin luster. Quartzite has Mohs hardness ~7 and no cleavage; marble has hardness ~3 and calcite cleavage—image alone cannot distinguish them.
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Physical properties
Smooth, rounded, pale gray-white, and fine-grained with a dull-to-satin luster. Quartzite has Mohs hardness ~7 and no cleavage; marble has hardness ~3 and calcite cleavage—image alone cannot distinguish them.
Formation & geological history
A tumbled specimen shaped by abrasion; quartzite formed when sandstone recrystallized, while marble formed when limestone metamorphosed. Their ages vary widely by deposit.
Uses & applications
Decorative stone, paperweight, craft material, and collector specimen; marble is also used in tiles and sculpture, while quartzite is used for countertops and aggregate.
Geological facts
A steel knife or glass-scratch test can help: quartzite generally scratches glass, whereas marble does not. A drop of dilute vinegar fizzes on calcite marble but not quartzite.
Field identification & locations
Common sources include Brazil, India, the United States, and Madagascar, but locality cannot be determined visually. Test hardness and acid reaction before assigning a precise identity.
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