sedimentary
Limestone
Calcium Carbonate (CaCO3)
Hardness: 3 on Mohs scale; Color: Grey, beige, or tan; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline calcite); Cleavage: Perfect rhombohedral but usually not visible in massive forms; Specific Gravity: 2.5-2.7
- Hardness
- 3 on Mohs scale
- Color
- Grey, beige, or tan
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: Grey, beige, or tan; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline calcite); Cleavage: Perfect rhombohedral but usually not visible in massive forms; Specific Gravity: 2.5-2.7
Formation & geological history
Formed primarily from the accumulation of shell, coral, algal, and fecal debris in marine environments. It can also form through chemical precipitation from lake or ocean water.
Uses & applications
Used extensively in construction as road base, aggregate for concrete, and as a raw material for cement and lime production. Highly valued for architectural facades and decorative stone.
Geological facts
Limestone covers about 10% of the Earth's total land surface. It is the primary rock found in karst landscapes, which are characterized by caves and sinkholes due to the rock's solubility in acidic water.
Field identification & locations
Identify in the field by its softness (can be scratched by a copper coin) and its effervescence (fizzing) when in contact with dilute hydrochloric acid or vinegar. Common in shallow marine deposits.
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