How to identify Quartz with Pyrite

To correctly identify Quartz with Pyrite (SiO2 (Quartz) with FeS2 (Pyrite)), 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

   Quartz: Colorless, white, gray, purple (amethyst), yellow (citrine), pink (rose quartz), brown (smoky quartz). Pyrite: Pale brass-yellow, metallic.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Quartz: Vitreous (glassy). Pyrite: Metallic.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Can range from massive intergrowths to well-formed quartz crystals hosting distinct pyrite crystals. Quartz can be granular, crystalline, or cryptocrystalline. Pyrite crystals are typically euhedral to subhedral.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Quartz: Hexagonal prisms terminated by rhombohedra. Pyrite: Cubes, pyritohedra, octahedra, often striated.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Quartz: None (conchoidal fracture). Pyrite: Indistinct on {001}.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Hydrothermal veins, porphyry deposits, volcanogenic massive sulfide (VMS) deposits, sedimentary rocks (as concretions or disseminations).

Key Facts

Hardness

Quartz: 7 on Mohs scale; Pyrite: 6-6.5 on Mohs scale.

Specific Gravity

Quartz: 2.65 g/cm³; Pyrite: 4.95-5.10 g/cm³.

Crystal System

Quartz: Trigonal; Pyrite: Isometric.

Color

Quartz: Colorless, white, gray, purple, yellow, pink, brown; Pyrite: Pale brass-yellow.

Luster

Quartz: Vitreous; Pyrite: Metallic.

Transparency

Quartz: Transparent to opaque; Pyrite: Opaque.

Fracture

Quartz: Conchoidal; Pyrite: Uneven to conchoidal.

Cleavage

Quartz: None; Pyrite: Indistinct on {001}.

Composition

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

Physical characteristics

• Crystal Habit: Quartz: Prismatic, massive, granular, cryptocrystalline; Pyrite: Cubic, pyritohedral, octahedral, massive, granular, radiating.
• Cleavage Type: Quartz: Absent; Pyrite: Indistinct.
• Fracture Type: Quartz: Conchoidal; Pyrite: Uneven to conchoidal.
• Tenacity: Quartz: Brittle; Pyrite: Brittle.
• Luster Type: Quartz: Vitreous; Pyrite: Metallic.

Explore Quartz with Pyrite