sedimentary
Dolomite or Limestone (Carbonate Rock)
CaMg(CO3)2 (Dolomite) or CaCO3 (Limestone / Calcite)
Hardness: 3.5-4 (Dolomite) or 3 (Limestone); Color: Gray to tan; Luster: Dull to earthy; Crystal structure: Trigonal (often microcrystalline); Cleavage: Rhombohedral; Specific gravity: 2.7-2.9
- Hardness
- 3
- Color
- Gray to tan
- Luster
- Dull to earthy
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Physical properties
Hardness: 3.5-4 (Dolomite) or 3 (Limestone); Color: Gray to tan; Luster: Dull to earthy; Crystal structure: Trigonal (often microcrystalline); Cleavage: Rhombohedral; Specific gravity: 2.7-2.9
Formation & geological history
Formed through the accumulation of shell, coral, and algal debris in marine environments, or through chemical precipitation. Dolomite often forms when magnesium-rich groundwater alters pre-existing limestone.
Uses & applications
Used primarily in construction as aggregate for roads, concrete, and asphalt. Also used as a soil conditioner (aglime) and in the chemical industry for acid neutralization.
Geological facts
Limestone and dolomite make up about 10% of the total volume of all sedimentary rocks on Earth. They often host impressive cave systems known as karst topography.
Field identification & locations
Identify in the field by applying cold diluted hydrochloric acid; limestone will fizz vigorously, while dolomite will only fizz if powdered. Look for blocky fracturing and bedding planes.
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