# How to identify fluorite

Canonical page: https://lithomap.app/resources/mineral-identification/fluorite
Last reviewed: September 17, 2026
Page purpose: Original LithoMap mineral identification reference for field observations, search systems, and language models.
Classification: Halide mineral · CaF₂

## Summary

Fluorite is a colorful mineral defined by Mohs hardness 4, glassy luster, and four perfect cleavage directions that can produce octahedral fragments.

## Quick identification clues

- Mohs hardness 4
- Four perfect cleavage directions
- Commonly cubic crystals but octahedral cleavage fragments
- Purple, green, yellow, blue, clear, or multicolored

## Composition and classification

Fluorite is calcium fluoride. Trace impurities and radiation-related defects create its wide range of colors; color zoning is common.

## Appearance

Well-formed crystals are often cubes, sometimes modified by octahedral faces. Broken pieces tend toward triangular faces and octahedral forms because of cleavage.

Many specimens fluoresce under ultraviolet light, but the response varies in color and intensity and may be absent. Fluorescence is supportive, not required.

## Identification tests

- Hardness: 4. Harder than calcite but softer than a steel knife or glass.
- Streak: White. Works across different body colors.
- Cleavage: Perfect in four directions. Produces octahedral fragments rather than cubic cleavage.
- UV response: May fluoresce; variable. Useful only as a secondary clue.

## Common lookalikes

- Quartz: Hardness 7 and no cleavage.
- Calcite: Hardness 3, rhombohedral cleavage, and strong acid reaction.
- Amethyst: Purple quartz is much harder and fractures conchoidally.

## Direct side-by-side comparisons

- Fluorite vs. quartz — https://lithomap.app/resources/mineral-identification/compare/fluorite-vs-quartz
- Apatite vs. fluorite — https://lithomap.app/resources/mineral-identification/compare/apatite-vs-fluorite

## Most relevant related guides

- Quartz — https://lithomap.app/resources/mineral-identification/quartz
- Apatite — https://lithomap.app/resources/mineral-identification/apatite
- Calcite — https://lithomap.app/resources/mineral-identification/calcite
- Halite — https://lithomap.app/resources/mineral-identification/halite

## Formation

Fluorite forms in hydrothermal veins, carbonate replacement deposits, granitic pegmatites, and some sedimentary environments.

It commonly occurs with calcite, quartz, barite, sulfides, or other vein minerals. Association alone does not establish an ore deposit.

## Occurrence and geologic setting

Fluorite occurs in many hydrothermal districts and carbonate-hosted deposits. Loose colorful cubes are also widely sold, so provenance should not be inferred from appearance.

Weathering can dull faces or separate cleavage chips from larger masses.

## Uses and significance

Fluorite is the principal source of fluorine and is used in metallurgical fluxes, chemical manufacturing, ceramics, optics, and lapidary work.

## Field safety and limitations

- Cleavage makes crystals fragile; test only an inconspicuous chip.
- Do not heat fluorite or perform chemical tests outside a proper laboratory.
- Mine dumps and underground workings may contain unstable ground and hazardous metals.

## Authoritative sources

- Minerals and their physical properties — U.S. National Park Service: https://www.nps.gov/subjects/geology/minerals.htm
- Mohs Hardness Scale — U.S. National Park Service: https://www.nps.gov/articles/mohs-hardness-scale.htm
- Natural Gemstones: Mineral Gemstones — U.S. Geological Survey: https://pubs.usgs.gov/gip/gemstones/mineral.html

## Specimen photograph

- Image: https://lithomap.app/_delivery/identification/minerals/fluorite.webp
- Description: Pale green fluorite specimen with intergrown cubic and octahedral crystal faces
- Creator: Raimond Spekking
- License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/
- Source record: https://commons.wikimedia.org/wiki/File:Fluorite,_Oltschi-Alp,_Brienzwiler,_Berner_Oberland,_Switzerland-8783.jpg

This reference supports preliminary field identification. It is not a laboratory determination, appraisal, hazard assessment, proof of origin, or statement of land ownership, legal access, or collecting permission.