How to identify Amethyst Geode Fragment

To correctly identify Amethyst Geode Fragment (Quartz (SiO2) variety Amethyst), 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

   Ranges from pale lilac to deep violet, often with color zoning. The purple hue is distinctive.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) on crystal faces, dull to waxy on the outer geode shell.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Crystalline, with distinct hexagonal prisms and rhombohedral terminations on the inner surface. The outer surface is typically rough and botryoidal or mammillary.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Hexagonal prisms terminated by rhombohedra, often forming drusy linings within the geode cavity.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None (lacks cleavage). Exhibits conchoidal fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in volcanic rocks (basalts, andesites) where gas bubbles or voids have been filled by silica-rich hydrothermal solutions. Also occurs in some granitic pegmatites and metamorphic rocks.

Key Facts

Hardness

7 on the Mohs scale

Specific Gravity

2.65

Crystal System

Trigonal

Color

Purple, violet, lilac

Luster

Vitreous

Transparency

Transparent to translucent

Fracture

Conchoidal

Cleavage

None

Composition

Silicon dioxide (SiO2)

Physical characteristics

• Crystal Habit: Prismatic, often forming drusy linings within cavities; hexagonal prisms terminated by rhombohedra.
• Cleavage Type: None
• Fracture Type: Conchoidal
• Tenacity: Brittle
• Luster Type: Vitreous

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