metamorphic
Marble
Metamorphosed Limestone (mainly CaCO3)
Hardness: 3 on Mohs scale; Color: typically white, gray, or bluish; Luster: dull to pearly; Crystal structure: Trigonal/hexagonal (recrystallized calcite); Cleavage: Perfect rhombohedral in individual crystals; Specific gravity: 2.7
- Hardness
- 3 on Mohs scale
- Color
- typically white, gray, or bluish
- Luster
- dull to pearly
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Physical properties
Hardness: 3 on Mohs scale; Color: typically white, gray, or bluish; Luster: dull to pearly; Crystal structure: Trigonal/hexagonal (recrystallized calcite); Cleavage: Perfect rhombohedral in individual crystals; Specific gravity: 2.7
Formation & geological history
Formed when limestone is subjected to the heat and pressure of metamorphism, causing recrystallization of the original carbonate mineral grains. This can occur during regional metamorphism or near igneous intrusions.
Uses & applications
Used widely in construction as building stone, sculpture for fine art, crushed stone for road aggregate, and as a component in whitening agents or soil treatments.
Geological facts
Pure white marble is the result of metamorphism of a very pure limestone. The characteristic swirls and veins of colored marble are usually due to various mineral impurities such as clay, silt, sand, or iron oxides.
Field identification & locations
Identify by its crystalline appearance and by testing with diluted hydrochloric acid, which will cause it to effervesce (fizz). It can also be scratched by a steel knife but not by a fingernail.
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