metamorphic
Marble
Metamorphosed Limestone (main mineral: Calcite, CaCO3)
Hardness: 3 on Mohs scale; Color: typically white with grey or black veins (swirls of impurities); Luster: dull to vitreous (waxy when polished); Crystal Structure: Trigonal/Hexagonal; Cleavage: Perfect rhombohedral in individual crystals; Specific gravity: 2.7
- Hardness
- 3 on Mohs scale
- Luster
- dull to vitreous (waxy when polished)
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Physical properties
Hardness: 3 on Mohs scale; Color: typically white with grey or black veins (swirls of impurities); Luster: dull to vitreous (waxy when polished); Crystal Structure: Trigonal/Hexagonal; Cleavage: Perfect rhombohedral in individual crystals; Specific gravity: 2.7
Formation & geological history
Formed through the regional or contact metamorphism of sedimentary limestone or dolostone. Under extreme heat and pressure, the calcite crystals recrystallize into a dense, interlocking mosaic of carbonate crystals. It can be found in mountain ranges and areas with ancient tectonic activity.
Uses & applications
Used extensively in construction (countertops, tiles), sculpture (white marble is preferred), chemical industry (as a source of calcium carbonate), and as an architectural aggregate. Low-grade specimens are crushed for road sub-base.
Geological facts
Pure white marble is the result of metamorphism of very pure limestone. The colorful swirls (veining) are caused by mineral impurities such as clay, silt, sand, or iron oxides that were present in the original limestone.
Field identification & locations
Identify in the field by its softness (can be scratched by a steel knife) and its reaction to dilute hydrochloric acid (it will fizz/effervesce). It is commonly found in quarries globally, notably in Italy (Carrara), Greece, and various parts of the Appalachian and Rocky Mountains.
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