Key properties
| Chemical formula | CaF2 |
| Crystal system | Cubic |
| Mohs hardness | 4 |
| Toughness | Poor (perfect cleavage and brittle) |
| Refractive index | 1.434 |
| Optic character | Singly refractive (isotropic) |
| Dispersion | 0.0070 |
| Specific gravity | 3.00-3.25 |
| Cleavage | Perfect in four directions (octahedral {111}) |
| Fracture | Subconchoidal to uneven; often step-like where cleavage shows |
| Habit | Well-formed cubes and octahedra; also massive, banded and botryoidal |
| Lustre | Vitreous to subvitreous; polish: Vitreous |
| UV fluorescence | Variable but often strong - the word fluorescence comes from fluorite; most gem material glows blue to violet (divalent europium is the classic cause in English material). |
| Pleochroism | None (isotropic) |
| Cause of colour | Colour centres in the crystal lattice (defects plus trace rare-earth elements such as yttrium and cerium) colour fluorite; pure CaF2 is colourless. Different centre types yield purple, blue, green and yellow. |
| Typical inclusions | Sharp colour zoning and banding, two- and three-phase inclusions, healed fractures; intergrown crystals in massive material |
| Stability | Very heat sensitive (cracks along cleavage); most colours stable to light but some fade with prolonged exposure; decomposed by sulfuric acid |
| Heat sensitivity | Very high - avoid any heat |
| Care and cleaning | Warm soapy water only; never ultrasonic or steam; avoid acids and heat |
| Availability | Plentiful rough but rarely seen in finished jewellery - mainly carvings, beads and collector specimens |
| Recognition | RI 1.434 (the lowest common gemstone RI), singly refractive, SG near 3.18, hardness 4 with four perfect cleavages, plus strong colour zoning and frequent fluorescence - a quick identification. |
Varieties (5)
Purple Fluorite
| Colour | purple to violet, often banded |
| Transparency | transparent to translucent |
| Clarity type | Type II to III (typically included and zoned) |
| Phenomena | Colour change in some stones (blue daylight to purple incandescent); thermoluminescence (chlorophane) |
| Appearance | Rich grape-jelly purple, frequently in sharp geometric bands with white, violet or green zones; faceted stones glow with an amethyst-like depth but far less durability. |
| Trade names | Blue John (banded purple-blue massive, Derbyshire) • chlorophane (thermoluminescent) |
| Misnomers | 'false amethyst' (historical) |
| Typical sizes | Clean facets to about 125 ct; carvings and beads in any size |
| Cutting styles | Carvings and beads overwhelmingly; occasionally faceted for collectors |
| Key separations | vs amethyst: RI 1.434 SR vs 1.544-1.553 DR, hardness 4 vs 7; vs purple glass: fluorite shows cleavage steps, zoning and lower SG? (glass SG varies) - use RI and hardness; vs scapolite: scapolite is DR with higher RI |
| Sources (localities) | China (leading) • England (Derbyshire Blue John) • Mexico • USA (Illinois) • Namibia • Germany • Switzerland • Norway • Spain |
| Availability | Plentiful rough; finished gems mainly carvings and beads |
| Market notes | Very inexpensive; Blue John ornamental pieces carry heritage premiums |
| Care notes | Warm soapy water; never ultrasonic or steam; keep from heat, acids and long strong light |
| In short | Purple fluorite offers amethyst-like richness with dramatic zoning at a fraction of the cost - and a fraction of the durability. Blue John banded material from Derbyshire is the ornamental classic. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–10.00 | $2.00 – $25.00 | commercial to collector | 2026-10-26 |
| 10.00–125.00 | $3.00 – $40.00 | collector | 2026-10-26 |
Retail market survey, per carat unless noted. Ranges describe what commercial to fine stones trade at; exceptional stones and provenance premiums sit above them.
Blue Fluorite
| Colour | blue to violetish blue |
| Transparency | transparent to translucent |
| Clarity type | Type II to III (typically included and zoned) |
| Phenomena | Colour change in some blue stones |
| Appearance | Clear sky-blue to deep aqua crystals and cabs, sometimes banded with purple; faceted pieces resemble blue topaz or aquamarine glass but with a distinctly softer, waxier facet polish. |
| Trade names | blue fluorite |
| Misnomers | sold occasionally as 'aqua-mariene' style fantasy names - it is not aquamarine |
| Typical sizes | 1 to 100+ ct rough abundant; clean facets under 20 ct usual |
| Cutting styles | Carvings, beads, spheres; rare faceting |
| Key separations | vs aquamarine: RI 1.434 SR vs 1.577-1.583 DR; vs blue topaz: RI 1.61-1.64 DR; vs synthetic blue spinel: RI 1.72-1.73 and much higher SG; fluorite's 1.434 spot reading is diagnostic alone |
| Sources (localities) | England • China • USA (Illinois) • Germany • Switzerland • Namibia |
| Availability | Available as specimens and carvings; faceted material intermittent |
| Market notes | Inexpensive collector gem; colour-zoned spheres and carvings dominate |
| Care notes | Warm soapy water; never heat, ultrasonic or steam |
| In short | Blue fluorite delivers serene aqua colour with the lowest RI in gemology. Beautiful in carvings, it is too soft and cleavage-prone for everyday rings. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–10.00 | $3.00 – $30.00 | commercial to collector | 2026-10-26 |
Retail market survey, per carat unless noted. Ranges describe what commercial to fine stones trade at; exceptional stones and provenance premiums sit above them.
Green Fluorite
| Colour | green to yellowish green |
| Transparency | transparent to translucent |
| Clarity type | Type II to III (typically included and zoned) |
| Phenomena | Occasional colour change |
| Appearance | Fresh spring green to deep emerald-like green, commonly interbanded with purple; faceted stones resemble fine emerald or tsavorite glass simulants but with far softer edges. |
| Trade names | green fluorite |
| Misnomers | 'South African emerald' style names are fraudulent - it is fluorite |
| Typical sizes | Facets commonly 1-30 ct; giant carving rough available |
| Cutting styles | Carvings, beads, spheres, occasional facets |
| Key separations | vs emerald or tsavorite: RI 1.434 SR is far below beryl (1.57-1.59) or garnet (1.74); vs green glass: fluorite shows perfect cleavage steps and zoning; vs peridot: peridot RI 1.65-1.69 DR and higher SG |
| Sources (localities) | Namibia (Okorusu) • China • England • Mexico • Norway • Switzerland |
| Availability | Common as specimens and carving rough |
| Market notes | Very inexpensive; spheres and towers dominate the ornamental trade |
| Care notes | Warm soapy water; avoid heat, acids and rough wear |
| In short | Green fluorite provides emerald-like colour in an affordable collector stone, easily confirmed by its 1.434 RI and softness. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–10.00 | $2.00 – $25.00 | commercial to collector | 2026-10-26 |
Retail market survey, per carat unless noted. Ranges describe what commercial to fine stones trade at; exceptional stones and provenance premiums sit above them.
Yellow Fluorite
| Colour | yellow to orange-yellow |
| Transparency | transparent to translucent |
| Clarity type | Type II to III (typically included and zoned) |
| Phenomena | Occasional colour change |
| Appearance | Warm honey-yellow to orange, often zoned with purple; faceted gems resemble citrine or yellow glass but with softer facet edges. |
| Trade names | yellow fluorite |
| Misnomers | rarely passed off as topaz or citrine |
| Typical sizes | 1-50 ct facets possible from large rough |
| Cutting styles | Carvings, beads; occasional faceting |
| Key separations | vs citrine: RI 1.434 SR vs 1.544-1.553 DR; vs yellow topaz: topaz RI 1.61-1.64 with 8 hardness; vs glass: fluorite cleaves and zones |
| Sources (localities) | England • Germany • Mexico • Switzerland • USA |
| Availability | Specimen rough common; faceted stones scarce |
| Market notes | Inexpensive collector gem |
| Care notes | Warm soapy water; no heat, ultrasonic or steam |
| In short | Yellow fluorite is a honey-toned collector gem whose oxygen-related colour centres and 1.434 RI make it both attractive and easy to identify. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–10.00 | $2.00 – $20.00 | commercial to collector | 2026-10-26 |
Retail market survey, per carat unless noted. Ranges describe what commercial to fine stones trade at; exceptional stones and provenance premiums sit above them.
Colourless Fluorite
| Colour | colourless to white |
| Transparency | transparent to translucent |
| Clarity type | Type II (typically included) |
| Phenomena | Fluorescence and phosphorescence; rare colour change |
| Appearance | Water-clear crystals with glassy faces, sometimes tinted faintly by adjacent colour zones; faceted stones are brilliantly low-dispersion and completely colourless. |
| Trade names | clear fluorite • optical fluorite (high-purity technical material) |
| Misnomers | sometimes sold as 'optical white quartz' - it is fluorite |
| Typical sizes | Clean facets of several carats from large crystals |
| Cutting styles | Rarely faceted; specimens and carvings preferred |
| Key separations | vs colourless quartz: RI 1.434 SR vs 1.544-1.553 DR; vs glass: fluorite cleaves in four directions and fluoresces strongly |
| Sources (localities) | England • USA • Switzerland • China |
| Availability | Specimens common, gems rare |
| Market notes | Minimal value; mainly of technical (optical) and collector interest |
| Care notes | Warm soapy water; avoid heat |
| In short | Colourless fluorite is the pure, uncontaminated end of the species - prized more by optical engineers and collectors than by jewellers. Its fluorescence is often spectacular. |
| Size (ct) | USD per carat | Tier | As of |
|---|---|---|---|
| 1.00–10.00 | $2.00 – $15.00 | collector | 2026-10-26 |
Retail market survey, per carat unless noted. Ranges describe what commercial to fine stones trade at; exceptional stones and provenance premiums sit above them.
Sources
· mindat.org · Wikipedia
Data compiled and fact-checked against gemmological literature, October 2026 (JDMIS gem reference). Properties are ranges accepted in gemmological practice; individual stones vary.
See also
Gemstone reference entries: gem #19 · gem #35 · gem #51 · gem #80 · gem #123 · gem #177
Related materials: Corundum · Diamond · Opal · Quartz · Spinel · Topaz
Identification wizard · All 83 materials · Singapore gem labs