How to identify Dolomite

To correctly identify Dolomite (CaMg(CO3)2), check each of these features in order. Many rocks and minerals look alike, so cross-reference multiple properties before deciding.

Step-by-step identification

1. 1

   Color

   Overall color and any zoning or banding

   Typically white, gray, pink, or tan; can also be colorless, green, brown, or black due to impurities.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous to pearly.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Often granular in dolostone; individual crystals can be rhombohedral with curved faces.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Usually forms rhombohedral crystals, often with curved or saddle-shaped faces. Also occurs as granular masses, massive, or columnar aggregates.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Perfect rhombohedral cleavage in three directions, producing fragments with angles of 73° and 107°.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in extensive sedimentary beds, often associated with evaporites, chert, and gypsum. Also occurs in hydrothermal veins, metamorphic rocks (dolomitic marbles), and as a gangue mineral.

Key Facts

Hardness

3.5-4 on Mohs scale

Specific Gravity

2.85 g/cm³

Crystal System

Trigonal

Color

White, gray, pink, tan, colorless, green, brown, black

Luster

Vitreous to pearly

Transparency

Transparent to translucent

Fracture

Conchoidal to uneven

Cleavage

Perfect rhombohedral in three directions at 73° and 107°

Composition

Calcium magnesium carbonate (CaMg(CO3)2)

Physical characteristics

• Crystal Habit: Typically rhombohedral, often with curved or saddle-shaped faces; also massive, granular, columnar.
• Cleavage Type: Perfect rhombohedral {1011}
• Fracture Type: Conchoidal to uneven
• Tenacity: Brittle
• Luster Type: Vitreous to pearly

Explore Dolomite