How to identify Quartz with Pyrite
SiO2 with FeS2
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Open the appTo correctly identify Quartz with Pyrite (SiO2 with FeS2), 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
Color
Overall color and any zoning or banding
Quartz: Colorless, white, gray, purple, yellow, brown, black (depending on variety and impurities). Pyrite: Pale brass-yellow, metallic.
- 2
Luster
How the surface reflects light: metallic, vitreous, dull
Quartz: Vitreous (glassy) to greasy. Pyrite: Metallic.
- 3
Texture
Grain size and surface feel: coarse, fine, glassy
Quartz: Crystalline, granular, massive. Pyrite: Crystalline, granular, massive, often forming distinct euhedral crystals within quartz.
- 4
Crystal Form
Shape of visible crystals or crystal faces
Quartz: Hexagonal prisms terminating in rhombohedra, massive, granular. Pyrite: Cubic, octahedral, pyritohedral, massive, granular.
- 5
Cleavage
How it breaks: flat cleavage planes vs irregular fracture
Quartz: None (conchoidal fracture). Pyrite: Indistinct on {100} (poor).
- 6
Geological Environment
The rock formation and setting where it occurs
Hydrothermal veins, metamorphic rocks, sedimentary rocks, often associated with ore deposits (especially gold, copper, lead-zinc).
Key Facts
- Hardness
- Quartz: 7 (Mohs); Pyrite: 6-6.5 (Mohs)
- 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, various; Pyrite: Pale brass-yellow
- Luster
- Quartz: Vitreous to greasy; Pyrite: Metallic
- Transparency
- Quartz: Transparent to opaque; Pyrite: Opaque
- Fracture
- Quartz: Conchoidal; Pyrite: Uneven to conchoidal
- Cleavage
- Quartz: None; Pyrite: Indistinct on {100}
- Composition
- Quartz: Silicon dioxide (SiO2); Pyrite: Iron disulfide (FeS2)
Physical characteristics
- Crystal Habit: Quartz: Prismatic, massive, granular; Pyrite: Cubic, octahedral, pyritohedral, massive, granular, radiating
- Cleavage Type: Quartz: Absent; Pyrite: Poor/indistinct
- Fracture Type: Quartz: Conchoidal; Pyrite: Uneven to conchoidal
- Tenacity: Quartz: Brittle; Pyrite: Brittle
- Luster Type: Quartz: Vitreous to greasy; Pyrite: Metallic
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