How to identify Anthracite with Quartz

To correctly identify Anthracite with Quartz (Anthracite (a variety of coal) with Quartz (SiO2)), 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

   Anthracite: Jet-black. Quartz: Typically colorless to white, sometimes translucent, but can be stained by impurities.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Anthracite: Submetallic to vitreous. Quartz: Vitreous.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Anthracite: Smooth, dense, often with conchoidal fracture surfaces. Quartz: Crystalline, granular, or massive within the vein.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Anthracite: Amorphous to cryptocrystalline (though it is not a true mineral). Quartz: Hexagonal prisms with pyramidal terminations, often anhedral (without well-formed faces) in veins.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Anthracite: None (exhibits conchoidal fracture). Quartz: None (exhibits conchoidal fracture).

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Anthracite forms in regions that have undergone significant tectonic compression and elevated temperatures, such as fold-and-thrust belts. Quartz veins are common in these environments, forming in fractures and faults within the coal seams and surrounding country rock due to hydrothermal activity or metamorphic fluid circulation.

Key Facts

Hardness

Anthracite: 2.5-2.75 (Mohs). Quartz: 7 (Mohs).

Specific Gravity

Anthracite: 1.3-1.7. Quartz: 2.65.

Crystal System

Anthracite: Amorphous to cryptocrystalline (not a true mineral, but a rock). Quartz: Trigonal (hexagonal system).

Color

Jet-black (anthracite); colorless, white, or translucent (quartz).

Luster

Submetallic to vitreous (anthracite); vitreous (quartz).

Transparency

Opaque (anthracite); transparent to translucent (quartz).

Fracture

Conchoidal (both anthracite and quartz).

Cleavage

None (both anthracite and quartz).

Composition

Anthracite: Primarily carbon (typically >90% fixed carbon), with minor volatile matter, ash, and moisture. Quartz: Silicon dioxide (SiO2).

Physical characteristics

• Crystal Habit: Anthracite: Massive, amorphous. Quartz: Prismatic, massive, granular.
• Cleavage Type: None for both.
• Fracture Type: Conchoidal for both.
• Tenacity: Brittle for both.
• Luster Type: Submetallic to vitreous (anthracite); Vitreous (quartz).

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