How to identify Dolomite

To correctly identify Dolomite (Dolomite), 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, pinkish, or yellowish. Can also be colorless, brown, or black.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous to pearly, especially on cleavage surfaces.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Fine-grained to coarsely crystalline. Often granular in dolostone. Individual mineral crystals can be rhombohedral.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Commonly forms rhombohedral crystals, often with curved faces (saddle-shaped). Also occurs as granular, 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 diamond-shaped faces.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in extensive sedimentary beds, often associated with evaporite deposits, ancient reef complexes, and platform carbonates. Also occurs in hydrothermal veins and as a gangue mineral in some ore deposits. Forms through diagenetic replacement of limestone or, less commonly, primary precipitation.

Key Facts

Hardness

3.5 - 4 on Mohs scale

Specific Gravity

2.85 - 2.95

Crystal System

Trigonal

Color

White, gray, pinkish, yellowish, colorless, 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: Rhombohedral, often with curved faces (saddle-shaped), massive, granular, columnar
• Cleavage Type: Perfect rhombohedral {1011}
• Fracture Type: Conchoidal to uneven
• Tenacity: Brittle
• Luster Type: Vitreous to pearly

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