sedimentary
Crushed Limestone
Sedimentary Calcium Carbonate (CaCO3)
Hardness: 3 on Mohs scale; Color: Grey, white, or tan; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: Perfect rhombohedral (rarely visible in aggregate samples); Specific gravity: 2.3 to 2.7.
- Hardness
- 3 on Mohs scale
- Color
- Grey, white, or tan
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: Grey, white, or tan; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: Perfect rhombohedral (rarely visible in aggregate samples); Specific gravity: 2.3 to 2.7.
Formation & geological history
Formed through the accumulation of shell, coral, algal, and fecal debris in warm, shallow marine waters. Most limestone is organic in origin, though some precipitates chemically from seawater.
Uses & applications
Primary use is in construction as road base, aggregate for concrete, and railroad ballast. Also used as a flux in steel making, a soil conditioner in agriculture, and in the production of cement and lime.
Geological facts
Limestone covers approximately 10% of the Earth's land surface. It is the primary rock type found in 'Karst' topography, characterized by caves, sinkholes, and underground drainage systems.
Field identification & locations
Can be identified in the field by its softness (scratched by a copper penny or steel knife) and its reaction to dilute hydrochloric acid (it will fizz or effervesce). Common in sedimentary basins worldwide.
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