How to identify Pyrite in Quartz Vein

To correctly identify Pyrite in Quartz Vein (FeS2 (Pyrite) and SiO2 (Quartz)), 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

   Pyrite: Brassy yellow to golden yellow, often with a metallic sheen. Quartz: Typically colorless, white, or milky white, but can be gray, pink, purple, or other colors due to impurities.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Pyrite: Metallic, bright. Quartz: Vitreous (glassy) to greasy.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Pyrite: Crystalline, often euhedral (well-formed) crystals. Quartz: Crystalline, massive, granular, or drusy.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Pyrite: Commonly cubic, octahedral, or pyritohedral crystals, sometimes striated. Quartz: Hexagonal prisms terminated by rhombohedra, often massive or anhedral within veins.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Pyrite: Indistinct to poor on {100}. Quartz: None (conchoidal fracture).

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Hydrothermal veins, often associated with igneous intrusions, metamorphic terrains, and sedimentary rocks that have undergone fluid alteration. Found in a wide range of ore deposits, including gold, copper, and lead-zinc deposits.

Key Facts

Hardness

Pyrite: 6-6.5 (Mohs); Quartz: 7 (Mohs)

Specific Gravity

Pyrite: 4.95-5.10; Quartz: 2.65

Crystal System

Pyrite: Isometric; Quartz: Trigonal

Color

Pyrite: Brassy yellow; Quartz: Colorless, white, various

Luster

Pyrite: Metallic; Quartz: Vitreous to greasy

Transparency

Pyrite: Opaque; Quartz: Transparent to translucent

Fracture

Pyrite: Uneven to conchoidal; Quartz: Conchoidal

Cleavage

Pyrite: Indistinct to poor; Quartz: None

Composition

Pyrite: Iron disulfide (FeS2); Quartz: Silicon dioxide (SiO2)

Physical characteristics

• Crystal Habit: Pyrite: Cubes, octahedra, pyritohedra, massive, granular, radiating; Quartz: Prismatic, massive, granular, cryptocrystalline
• Cleavage Type: Pyrite: Indistinct to poor {100}; Quartz: None
• Fracture Type: Pyrite: Uneven to conchoidal; Quartz: Conchoidal
• Tenacity: Pyrite: Brittle; Quartz: Brittle
• Luster Type: Pyrite: Metallic; Quartz: Vitreous to greasy

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