sedimentary
Limestone Cobble
Carbonate Rock (CaCO3)
Hardness: 3-4 (Mohs scale); Color: Gray to light tan; Luster: Dull/Earthy; Structure: Fine-grained with visible calcite veins; Cleavage: None (conchoidal fracture).
- Hardness
- 3-4 (Mohs scale)
- Color
- Gray to light tan
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3-4 (Mohs scale); Color: Gray to light tan; Luster: Dull/Earthy; Structure: Fine-grained with visible calcite veins; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed from the accumulation of calcium carbonate (shells, coral, algal debris) in shallow marine environments. This specimen has been rounded by fluvial or glacial transport.
Uses & applications
Construction aggregate, cement production, soil conditioner (lime), and industrial chemical stabilizer.
Geological facts
Limestone covers about 10% of the Earth's land surface. It is the primary rock type in karst landscapes, known for creating dramatic caves and sinkholes.
Field identification & locations
Identify in the field by its readiness to fizz when exposed to weak acid (HCl). This specimen shows typical quartz or calcite micro-veins filling old fractures.
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