How to identify Fluorite in Quartz

To correctly identify Fluorite in Quartz (Fluorite (CaF2) and Quartz (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

   Quartz is typically colorless, white, or translucent, but can be various colors (e.g., purple amethyst, yellow citrine, smoky quartz). Fluorite exhibits a wide range of colors including purple, green, blue, yellow, pink, and colorless. The contrast in color between the two minerals is often a key identifier.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Quartz has a vitreous (glassy) luster. Fluorite also has a vitreous luster.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   The texture will depend on the crystal habits and growth patterns. Quartz can be massive, granular, or euhedral. Fluorite often forms well-defined cubic, octahedral, or dodecahedral crystals, or massive aggregates.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Quartz typically forms hexagonal prisms with pyramidal terminations. Fluorite commonly forms cubic crystals, often modified by octahedral or dodecahedral faces. The distinct crystal forms are crucial for identification.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Quartz has no cleavage, exhibiting conchoidal fracture. Fluorite has perfect octahedral cleavage in four directions, which is a very distinctive characteristic.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Hydrothermal veins, pegmatites, and greisens are common environments. Often found in association with metallic ore deposits (e.g., lead, zinc, silver) due to shared hydrothermal origins.

Key Facts

Hardness

Quartz: 7 on Mohs scale; Fluorite: 4 on Mohs scale. This difference is crucial for identification.

Specific Gravity

Quartz: 2.65 g/cm³; Fluorite: 3.18 g/cm³.

Crystal System

Quartz: Trigonal; Fluorite: Isometric (Cubic).

Color

Quartz: Colorless, white, purple, pink, brown, black, green, red, yellow, blue; Fluorite: Purple, green, blue, yellow, pink, colorless, brown, black.

Luster

Vitreous (glassy) for both.

Transparency

Quartz: Transparent to translucent; Fluorite: Transparent to translucent.

Fracture

Quartz: Conchoidal; Fluorite: Uneven to subconchoidal.

Cleavage

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

Composition

Quartz: Silicon dioxide (SiO2); Fluorite: Calcium fluoride (CaF2).

Physical characteristics

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

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