sedimentary
Limestone
Calcium Carbonate (CaCO3)
Hardness: 3 on Mohs scale. Color: Light grey to brownish-tan due to iron oxide staining. Luster: Dull, earthy. Structure: Microcrystalline to fine-grained. Cleavage: None (conchoidal to irregular fracture). Specific gravity: 2.5–2.7.
- Hardness
- 3 on Mohs scale
- Color
- Light grey to brownish-tan due to iron oxide staining
- Luster
- Dull, earthy
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Physical properties
Hardness: 3 on Mohs scale. Color: Light grey to brownish-tan due to iron oxide staining. Luster: Dull, earthy. Structure: Microcrystalline to fine-grained. Cleavage: None (conchoidal to irregular fracture). Specific gravity: 2.5–2.7.
Formation & geological history
Formed in shallow, calm, warm marine waters by the accumulation and compaction of shells, coral, algal, and fecal debris, or chemical precipitation of calcium carbonate.
Uses & applications
Widely used as a aggregate in construction, manufacturing of cement and lime, soil conditioner in agriculture, and neutralizer in chemical processing.
Geological facts
Limestone effervesces (fizzes) strongly when exposed to dilute hydrochloric acid. Over 10% of all sedimentary rocks on Earth are limestones.
Field identification & locations
Easily identified by testing with a drop of acid or vineger to observe fizzing. It is soft enough to be scratched by a steel nail. Commonly found near ancient seabed exposures and riverbeds.
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