sedimentary
Limestone (likely weathered)
Limestone (Mainly Calcium Carbonate, CaCO3)
Hardness: 3 (Mohs scale); Color: Gray, tan, and brown; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: None visible in hand sample; Specific gravity: 2.3-2.7
- Hardness
- 3 (Mohs scale)
- Color
- Gray, tan, and brown
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 (Mohs scale); Color: Gray, tan, and brown; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: None visible in hand sample; Specific gravity: 2.3-2.7
Formation & geological history
Formed by the accumulation of shell, coral, algal, and fecal debris in clear, warm, shallow marine waters. Can also form through the chemical precipitation of calcium carbonate from lake or ocean water.
Uses & applications
Primarily used in construction (crushed stone, cement), agriculture (lime), and as a base material in chemical industries.
Geological facts
Limestone is the most common carbonaceous sedimentary rock and can often contain fossils of ancient marine life. It is highly susceptible to acid rain, which dissolves the calcium carbonate over time.
Field identification & locations
Identified in the field by its softness (scratched by a copper penny or steel) and vigorous effervescence when exposed to dilute hydrochloric acid. Commonly found in karst landscapes and coastal regions.
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