How to identify Amethyst with Pyrite

To correctly identify Amethyst with Pyrite (SiO2 (Amethyst) 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

   Amethyst: Purple (ranging from pale lilac to deep violet). Pyrite: Pale brass-yellow, metallic.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Amethyst: Vitreous (glassy). Pyrite: Metallic.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Amethyst: Smooth, often euhedral crystal faces. Pyrite: Smooth, often euhedral crystal faces, sometimes granular or massive.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Amethyst: Hexagonal prisms terminated by rhombohedral faces, often forming drusy coatings or larger individual crystals. Pyrite: Cubic, pyritohedral, or octahedral crystals, sometimes massive or granular.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

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

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Hydrothermal veins, vugs, and geodes within igneous (especially volcanic basalts and rhyolites) and metamorphic rocks. Often found in areas with significant past or present hydrothermal activity.

Key Facts

Hardness

Amethyst: 7 on Mohs scale. Pyrite: 6-6.5 on Mohs scale.

Specific Gravity

Amethyst: 2.65 g/cm³. Pyrite: 4.95-5.10 g/cm³.

Crystal System

Amethyst: Trigonal. Pyrite: Isometric (Cubic).

Color

Amethyst: Purple. Pyrite: Pale brass-yellow.

Luster

Amethyst: Vitreous. Pyrite: Metallic.

Transparency

Amethyst: Transparent to translucent. Pyrite: Opaque.

Fracture

Amethyst: Conchoidal. Pyrite: Uneven to conchoidal.

Cleavage

Amethyst: None. Pyrite: Indistinct on {001}.

Composition

Amethyst: Silicon dioxide (SiO2). Pyrite: Iron disulfide (FeS2).

Physical characteristics

• Crystal Habit: Amethyst: Prismatic, often terminated by rhombohedra, drusy. Pyrite: Cubic, pyritohedral, octahedral, massive, granular.
• Cleavage Type: Amethyst: Absent. Pyrite: Indistinct.
• Fracture Type: Amethyst: Conchoidal. Pyrite: Uneven to conchoidal.
• Tenacity: Amethyst: Brittle. Pyrite: Brittle.
• Luster Type: Amethyst: Vitreous. Pyrite: Metallic.

Explore Amethyst with Pyrite