sedimentary
Limestone
Sedimentary Calcite (CaCO3)
Hardness: 3 on Mohs scale; Color: Gray, tan, or white; Luster: Dull to earthy; Crystal Structure: Trigonal (microcrystalline); Cleavage: Perfect rhombohedral in crystals, but generally massive in rock form; Specific Gravity: 2.7.
- Hardness
- 3 on Mohs scale
- Color
- Gray, tan, or white
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: Gray, tan, or white; Luster: Dull to earthy; Crystal Structure: Trigonal (microcrystalline); Cleavage: Perfect rhombohedral in crystals, but generally massive in rock form; Specific Gravity: 2.7.
Formation & geological history
Formed primarily from the accumulation of shell, coral, algal, and fecal debris in marine environments. It can also form through the chemical precipitation of calcium carbonate from lake or ocean water.
Uses & applications
Widely used as building stone, in the production of cement/concrete, as a soil conditioner in agriculture, and as a raw material for the chemical industry to produce lime.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary source of 'fossil fuels' indicators and often contains well-preserved fossils of ancient sea life.
Field identification & locations
Identify in the field by its softness (can be scratched by a copper penny or steel knife) and its strong effervescent reaction when exposed to cold dilute hydrochloric acid (vinegar can also cause faint bubbling).
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