How to identify Bituminous Coal

To correctly identify Bituminous Coal (Bituminous Coal), 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 black, sometimes very dark brown.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) to dull, often with a greasy or pitch-like appearance. Bright bands (vitrain) are vitreous, while dull bands (durain) are dull or earthy.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Often banded, with alternating bright and dull layers. Can be brittle and friable, breaking into blocky or irregular fragments. May show fossil plant impressions.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Amorphous; does not form crystals. Occurs as massive, layered, or blocky aggregates.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   No true mineral cleavage. Exhibits a characteristic 'blocky' or 'cubical' fracture pattern, often with jointing perpendicular to bedding planes.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in sedimentary basins, typically within sequences of shale, sandstone, and sometimes limestone. Forms in ancient swamp or bog environments that were subsequently buried and subjected to coalification. Often associated with deltaic, fluvial, or lacustrine depositional settings.

Key Facts

Hardness

1.0-2.5 (Mohs scale) - very soft and easily scratched.

Specific Gravity

1.2-1.5 g/cm³ (variable depending on ash content and moisture).

Crystal System

Amorphous (non-crystalline).

Color

Black, sometimes dark brown.

Luster

Vitreous, sub-vitreous, dull, or greasy.

Transparency

Opaque.

Fracture

Conchoidal to irregular, often blocky or cubical.

Cleavage

None (exhibits jointing or 'cleat' planes, not true mineral cleavage).

Composition

Primarily carbon (45-86% dry, ash-free basis), with varying amounts of hydrogen, oxygen, nitrogen, sulfur, and inorganic ash-forming minerals (e.g., clays, quartz, pyrite).

Physical characteristics

• Crystal Habit: Massive, layered, or blocky aggregates; no distinct crystal form.
• Cleavage Type: None (exhibits 'cleat' - a system of natural fractures or joints, typically orthogonal, which aids in mining).
• Fracture Type: Conchoidal to irregular, often blocky.
• Tenacity: Brittle.
• Luster Type: Vitreous (bright bands), dull (dull bands), greasy, or pitch-like.

Explore Bituminous Coal