metamorphic
Tumbled limestone or marble fragment
Calcite (CaCO₃), likely marble; possibly compact limestone
AI-generated identification · may be incorrectCream-white, fine-grained, dull to softly waxy luster, rounded and smoothed surface; calcite hardness Mohs 3, with irregular fracture and no obvious cleavage visible. It should fizz with dilute hydrochloric acid or strong vinegar if exposed fresh.
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Physical properties
Cream-white, fine-grained, dull to softly waxy luster, rounded and smoothed surface; calcite hardness Mohs 3, with irregular fracture and no obvious cleavage visible. It should fizz with dilute hydrochloric acid or strong vinegar if exposed fresh.
Formation & geological history
If marble, it formed when limestone recrystallized under heat and pressure during metamorphism; if limestone, it is sedimentary carbonate rock formed from marine carbonate mud or shells. Precise age and identity cannot be determined from the photograph.
Uses & applications
Used as aggregate, dimension stone, cement feedstock, and decorative stone; attractive polished pieces may be used in crafts or small collections.
Geological facts
The smoothly curved shape appears human-tumbled or water-worn rather than naturally crystalline. Calcite is typically softer than quartz and can be scratched by a steel knife.
Field identification & locations
Common in carbonate terrains worldwide, including Italy, Greece, Turkey, Mexico, and the United States. Test acid reaction, hardness, and powder color; a polished white pebble could also be bone or another carbonate material.
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