sedimentary
Limestone
Calcium Carbonate (CaCO3)
Hardness: 3 on Mohs scale; Color: typically white, gray, or tan; Luster: dull to earthy; Crystal structure: Trigonal (as calcite); Cleavage: Perfect rhombohedral in calcite form; Specific gravity: 2.7.
- Hardness
- 3 on Mohs scale
- Color
- typically white, gray, or tan
- Luster
- dull to earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: typically white, gray, or tan; Luster: dull to earthy; Crystal structure: Trigonal (as calcite); Cleavage: Perfect rhombohedral in calcite form; Specific gravity: 2.7.
Formation & geological history
Formed in marine environments through the accumulation of shell, coral, algal, and fecal debris. It can also be precipitated directly from water in caves or springs. Geological age varies from Precambrian to Holocene.
Uses & applications
Widely used in construction for aggregate, building stone, cement manufacture, and as a soil conditioner in agriculture. It is also used to manufacture glass and refine metals.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary building material for the Great Pyramids of Giza.
Field identification & locations
Identify in the field by its softness (can be scratched by a copper coin) and its effervescence (fizzing) when reacting with dilute hydrochloric acid. Commonly found in ancient sea beds and karst landscapes.
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