metamorphic
Likely limestone or marble fragment
Calcite-rich carbonate rock; possibly marble (CaCO₃)
AI-generated identification · may be incorrectPale cream-white, dull to slightly sugary luster, massive and fine-grained with no obvious crystals. Calcite hardness is 3 Mohs; it should fizz vigorously with dilute hydrochloric acid or vinegar, while marble may show weaker reaction if recrystallized.
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Physical properties
Pale cream-white, dull to slightly sugary luster, massive and fine-grained with no obvious crystals. Calcite hardness is 3 Mohs; it should fizz vigorously with dilute hydrochloric acid or vinegar, while marble may show weaker reaction if recrystallized.
Formation & geological history
Likely formed from compacted marine carbonate sediment (limestone), or recrystallized during metamorphism into marble. Limestone commonly ranges from Precambrian to Recent; the specimen’s age cannot be determined visually.
Uses & applications
Used for aggregate, cement, lime, building stone, sculpture, and—if sufficiently attractive—interior decoration. Ordinary rough pieces generally have little commercial value.
Geological facts
The straight, planar faces suggest it may be a cut or broken building-stone sample rather than a naturally weathered rock. Calcite’s acid reaction and softness distinguish it from quartz-rich rocks.
Field identification & locations
Common in sedimentary basins and metamorphic belts worldwide, including the Alps, Appalachians, Carrara, and regions of China and India. Test a fresh surface with dilute acid, inspect grain size, and compare scratch resistance with a steel knife.
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