dolomite

Description: Dolomite is a common rock-forming mineral. It is very similar to Calcite, but is a magnesium carbonate; it’s the primary component of a sedimentary rock known as dolostone and the metamorphic rock called dolomitic marble. Limestone that contains some dolomite is known as dolomitic limestone.

Chemical Formula: CaMg(CO3)2

Crystal Form: none, microcrystalline quartz occurs in botryoidal, mammilary, stalactitic, massive, nodular forms, as smooth rounded pebbles, as banded masses, as amygdules, and as the linings of geodes.

Crystal System: Hexagonal

Color: Colorless, white, pink, green, gray, brown or black

Streak: White

Luster: Vitreous, pearly

Fracture: Conchoidal

Cleavage: Perfect, rhombahedral, three directions

Hardness: 3.5 - 4.0 on Moh's scale

Density/Specific Gravity: 2.7 g/cm3

Magnetism: N/A

Taste: N/A

Hydrochloric acid: N/A

Radioactivity: N/A

Fluorescence: Fluorescent dolomite has been reported (Franklin, NJ)

Distinguishing Physical Properties:

  • Hardness: it is harder than calcite - 3 ½ to 4

  • Acid: only mildly reactive to dilute acid, if pulverized

  • Similar properties to calcite

Photograph Attribution: Dolomite specimen photograph by Sean C. Murphy, 2020.