sedimentary
Limestone
Calcareous sedimentary rock (primarily Calcium Carbonate, CaCO3)
Hardness: 3-4 (Mohs); Color: White, buff, or light gray; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline calcite); Cleavage: None (rhombohedral in calcite crystals); Specific gravity: 2.5-2.7
- Hardness
- 3-4 (Mohs)
- Color
- White, buff, or light gray
- Luster
- Dull to earthy
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Physical properties
Hardness: 3-4 (Mohs); Color: White, buff, or light gray; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline calcite); Cleavage: None (rhombohedral in calcite crystals); Specific gravity: 2.5-2.7
Formation & geological history
Formed through the accumulation of shell, coral, algal, and fecal debris in marine environments, or by chemical precipitation from water. Formed across all geological eras from the Precambrian to present.
Uses & applications
Used widely as a building material, in the manufacture of cement and lime, as road base, and as a soil conditioner in agriculture.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary parent rock for caves and karst topography due to its solubility in slightly acidic water.
Field identification & locations
Identify in the field by its softness (can be scratched by a copper coin) and its effervescence (bubbles) when a drop of dilute hydrochloric acid is applied. Found worldwide in ancient seabed deposits.
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