sedimentary
Limestone (specifically Carboniferous Limestone)
Calcium Carbonate (CaCO3)
Hardness: 3 on Mohs scale; Color: Gray to bluish-gray; Luster: Dull to earthy; Crystal structure: Trigonal/Microcrystalline; Specific gravity: 2.7
- Hardness
- 3 on Mohs scale
- Color
- Gray to bluish-gray
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: Gray to bluish-gray; Luster: Dull to earthy; Crystal structure: Trigonal/Microcrystalline; Specific gravity: 2.7
Formation & geological history
Formed in warm, shallow marine environments through the accumulation of shell, coral, and algal debris. The gray color and texture are typical of Carboniferous aged deposits (approx. 300-360 million years old).
Uses & applications
Used primarily in construction for building stone, aggregate for concrete, manufacture of cement, and as a soil conditioner in agriculture.
Geological facts
Limestone often contains invisible micro-fossils and can be tested for identity using weak acid like vinegar, which will make it effervesce or fizz.
Field identification & locations
Identify in the field by its gray color, presence of calcite veins (white streaks), and its ability to be scratched by a steel nail. Found worldwide in ancient marine basins.
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