How to identify Fluorite with Quartz

To correctly identify Fluorite with Quartz (CaF2 with SiO2), 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

   Fluorite: Wide range including purple, green, blue, yellow, pink, brown, colorless, often banded. Quartz: Colorless, white, smoky, purple (amethyst), yellow (citrine), pink (rose quartz).

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Fluorite: Vitreous. Quartz: Vitreous to greasy.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Fluorite: Smooth, often with distinct crystal faces. Quartz: Smooth to slightly rough, often with striations on prism faces.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Fluorite: Typically cubic, octahedral, or dodecahedral crystals. Quartz: Hexagonal prisms terminated by rhombohedra (often appearing as pyramids).

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Fluorite: Perfect octahedral cleavage (four directions). Quartz: No cleavage, conchoidal fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Hydrothermal veins, pegmatites, greisens, and sedimentary rocks (especially limestones and dolomites where fluorite can replace carbonates). Often found in association with metallic ore deposits.

Key Facts

Hardness

Fluorite: 4 (Mohs); Quartz: 7 (Mohs)

Specific Gravity

Fluorite: 3.18 (variable with impurities); Quartz: 2.65

Crystal System

Fluorite: Isometric; Quartz: Trigonal

Color

Fluorite: Highly variable (purple, green, blue, yellow, colorless, etc.); Quartz: Colorless, white, smoky, purple, yellow, pink.

Luster

Vitreous

Transparency

Transparent to translucent

Fracture

Fluorite: Subconchoidal to uneven; Quartz: Conchoidal

Cleavage

Fluorite: Perfect octahedral (4 directions); Quartz: None

Composition

Fluorite: Calcium Fluoride (CaF2); Quartz: Silicon Dioxide (SiO2)

Physical characteristics

• Crystal Habit: Fluorite: Cubic, octahedral, dodecahedral, massive; Quartz: Prismatic (hexagonal), massive, granular.
• Cleavage Type: Fluorite: Perfect octahedral; Quartz: None.
• Fracture Type: Fluorite: Subconchoidal to uneven; Quartz: Conchoidal.
• Tenacity: Fluorite: Brittle; Quartz: Brittle.
• Luster Type: Vitreous (glassy) for both.

Explore Fluorite with Quartz