Dolomite

Chemical Formula

CaMg(CO₃)₂

Composition

Calcium magnesium carbonate. The amount of calcium and magnesium in most specimens is equal, but occasionally one element may have a slightly greater presence than the other. Small amounts of iron and manganese are sometimes also present.

Variable Formula

(Ca,Mg)₂(CO₃)₂
(Ca,Mg,Fe,Mn)₂(CO₃)₂

Color

Colorless, white, gray, peach, pink, yellow, and orange. Rarely yellow, green, red, and black.

Streak

White

Hardness

3.5 - 4

Crystal System

Hexagonal

3D Crystal Atlas
(Click for animated model) 

Crystal Forms 
and Aggregates

Common in groups of small rhombohedral crystals, often with curved, saddle-like faces. Also prismatic, (although usually slightly curved), grainy, botryoidal, coxcomb, and massive. Uncommon in large rhombohedrons or rhombohedral aggregates.
 

Transparency

Transparent to translucent

Specific Gravity

2.8 - 3.0

Luster

Vitreous, pearly

Cleavage

1,3 - rhombohedral

Fracture

Conchoidal

Tenacity

Brittle

Other ID Marks

Occasionally fluorescent bluish-white or pink in shortwave ultraviolet light.

Complex Tests

Effervesces in hydrochloric acid. Slowly dissolves in nitric acid and hydrochloric acids.

In Group

Carbonates;

Striking Features

Curved crystals and crystal groupings, associate minerals and environment

Environment

In sedimentary rock such as dolomite rock and limestones. Occasionally in high-temperature metamorphic rocks and low-temperature hydrothermal veins.
 

Rock Type

Igneous, Sedimentary, Metamorphic

Popularity (1-4)

2

Prevalence (1-3)

1

Demand (1-3)

1