metamorphic
Polished gray marble slab
Calcite-rich marble (recrystallized limestone; chiefly CaCO₃)
AI-generated identification · may be incorrectTypically Mohs 3, gray to white with cloudy veining, vitreous-to-satin luster, and interlocking calcite crystals; calcite shows rhombohedral cleavage and effervesces strongly with dilute hydrochloric acid. The slab appears cut and polished, with possible darker graphite, mica, or silicate impurities.
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Physical properties
Typically Mohs 3, gray to white with cloudy veining, vitreous-to-satin luster, and interlocking calcite crystals; calcite shows rhombohedral cleavage and effervesces strongly with dilute hydrochloric acid. The slab appears cut and polished, with possible darker graphite, mica, or silicate impurities.
Formation & geological history
Formed when limestone or dolostone was recrystallized under heat and pressure during regional or contact metamorphism, commonly from Paleozoic to Precambrian protoliths. Exact age and locality cannot be determined from the image.
Uses & applications
Used for tiles, countertops, monuments, sculpture, and architectural facing; attractive pieces are sold as decorative or lapidary specimens. It is generally less durable and acid-resistant than granite.
Geological facts
Marble’s calcite grains interlock during metamorphism, destroying most original fossils and sedimentary textures. Gray coloration commonly reflects carbonaceous material, graphite, pyrite, or other mineral impurities.
Field identification & locations
Identify by its relatively soft surface, calcite cleavage, and vigorous acid fizz; a steel blade may scratch it, unlike quartz-rich rocks. Common sources include Italy, Greece, Turkey, India, the United States, and Mexico.
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