sedimentary

Dolomite or Limestone (Carbonate Rock)

CaMg(CO3)2 (Dolomite) or CaCO3 (Limestone / Calcite)

AI-generated identification · may be incorrect

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

Identified April 9, 2026More sedimentary →

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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.