metamorphic
Marble
Metamorphosed Limestone (principally CaCO3)
Hardness: 3 on Mohs scale; Color: Pure white (may have gray or colored veins based on impurities like clay or iron oxides); Luster: Vitreous to pearly; Crystal structure: Trigonal/Hexagonal (calcite); Cleavage: Rhombohedral (observable in individual crystals); Specific gravity: 2.7
- Hardness
- 3 on Mohs scale
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 3 on Mohs scale; Color: Pure white (may have gray or colored veins based on impurities like clay or iron oxides); Luster: Vitreous to pearly; Crystal structure: Trigonal/Hexagonal (calcite); Cleavage: Rhombohedral (observable in individual crystals); Specific gravity: 2.7
Formation & geological history
Formed through the regional or contact metamorphism of sedimentary carbonate rocks, most commonly limestone or dolostone. This recrystallization process occurs under intense heat and pressure, typically during mountain-building events (orogeny).
Uses & applications
Used extensively in construction (tiles, countertops, flooring), sculpture, and architecture due to its relative softness and ability to take a high polish. Also used in crushed form as an agricultural soil treatment or as a calcium supplement in animal feed.
Geological facts
Marble is the medium of choice for many famous historical sculptures, such as Michelangelo's 'David.' It takes its name from the Greek word 'marmaros,' which means 'shining stone.' Unlike many other metamorphic rocks, marble is non-foliated, meaning it lacks a layered or banded appearance.
Field identification & locations
Identify in the field by its characteristic granular, sugary texture and the fact that it reacts (fizzes) with cold dilute hydrochloric acid. It is found globally in mountainous regions, notably in Carrara, Italy, and Vermont, USA. Collectors look for unique veining or specific colors indicative of rare impurities.
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