sedimentary
Limestone
Calcium Carbonate (CaCO3)
Hardness: 3 (Mohs scale); Color: White, grayish, tan; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (rhombohedral in calcite form); Specific Gravity: 2.3–2.7
- Hardness
- 3 (Mohs scale)
- Color
- White, grayish, tan
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 (Mohs scale); Color: White, grayish, tan; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (rhombohedral in calcite form); Specific Gravity: 2.3–2.7
Formation & geological history
Formed through the accumulation of shell, coral, algal, and fecal debris in warm, shallow marine waters. Can also form through chemical precipitation from ocean or lake water.
Uses & applications
Extensively used in construction as aggregate for concrete, road base, and architectural building stone. Also vital in manufacturing cement, steel, and as a soil conditioner in agriculture.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks on Earth. It often contains visible fossils of marine organisms like brachiopods and crinoids.
Field identification & locations
Identify in the field by its tendency to effervesce (fizz) when in contact with dilute hydrochloric acid. Commonly found in quarries and outcrops in regions that were once ancient sea beds.
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