Purple Fluorite: Color & Properties

Purple fluorite is the violet to deep-purple variety of the halide mineral fluorite (calcium fluoride, CaF₂). Its vivid color range—from pale lavender to royal purple—arises from trace elements such as yttrium and cerium, as well as from radiation-induced color centers within the crystal lattice. Fluorite crystallizes in an isometric (cubic) system, often forming well-defined cubes or octahedra. Collectors prize the purple variety not only for its striking hues but also for its relative rarity compared to other fluorite colors.

Formation and Coloration of Purple Fluorite

Purple fluorite (CaF₂) forms primarily in hydrothermal veins, where calcium- and fluorine-rich fluids move through fractures in rocks such as limestone, dolostone, or syenite. As fluids cool, fluorite crystallizes, typically as cubic or octahedral crystals. Crystallization temperatures vary—from ~80°C in sedimentary systems to >400°C in igneous settings—depending on the geological context.

Purple fluorite crystals with step-growth crystal habit, architectural zoning and precise geometric patterning. Photo by: Ghulam Mustafa.

Hydrothermal Deposit Types

Carbonate-Hosted Epigenetic Veins:

In regions like the Illinois-Kentucky Fluorspar District (USA) and Yiwu Mine (China), fluids leach calcium from carbonate host rocks. Interaction with fluorine-rich solutions precipitates fluorite in veins. Fluid inclusions indicate temperatures of 100–250°C.

Alkaline Igneous Associations:

In syenite and carbonatite systems, late-stage magmatic fluids enriched in fluorine interact with assimilated calcium, forming fluorite at 300–440°C. Coarse crystals are typical. Key examples: Okorusu (Namibia), Amba Dongar (India).

Sedimentary Exhalative (SEDEX) Systems:

Submarine hydrothermal vents discharge fluids onto the seafloor, precipitating stratabound fluorite layers at 80–120°C. Bacterial sulfate reduction provides sulfide ligands, influencing metal transport. Examples include the Zechstein Basin (Germany).

Purple fluorite under UV light, showcasing intense blue-violet fluorescence.

Coloration Mechanisms

Radiation-Induced Color Centers: Alpha particles from uranium- and thorium-bearing minerals displace fluoride ions, creating F-centers—electron vacancies that absorb visible light and generate the purple hue.

Rare Earth Element Substitution: Yttrium (Y³⁺), cerium (Ce³⁺), and other lanthanides substitute for Ca²⁺, introducing intermediate energy states that absorb green-yellow wavelengths, enhancing purple coloration via subtractive effects.

Nanoparticle Scattering: Colloidal calcium nanoparticles (<100 nm), especially in Cave-In-Rock specimens, produce Tyndall scattering. This causes perceptual shifts—from violet-blue in daylight to reddish-purple under incandescent light.

Fluorescence and Luminescence

Purple fluorite is well known for its strong fluorescence under ultraviolet light, typically glowing blue-violet due to activator ions such as Eu²⁺. Thermoluminescence experiments show that heating can temporarily enhance color by releasing trapped electrons, highlighting the dynamic nature of fluorite’s optical behavior.

Purple fluorite cluster with intergrown cubic crystals in a staircase formation.

Physical and Chemical Properties of Purple Fluorite

Chemical Properties

• Chemical Formula: CaF₂ — composed of one calcium ion (Ca²⁺) and two fluoride ions (F⁻).
• Elemental Composition: ~51.3% calcium and ~48.7% fluorine by weight.
• Solubility: Sparingly soluble in water; dissolves more readily in acids.
• Stability: Stable under ambient conditions; can be etched or dissolved by hydrofluoric acid.

Physical Properties

• Color: Pale lavender to deep violet due to trace impurities and radiation-induced color centers; zoning and banding are common.
• Crystal System: Isometric (cubic); typically forms cubic or octahedral crystals.
• Hardness: 4 on the Mohs scale—relatively soft and easily scratched.
• Cleavage: Perfect octahedral cleavage in four directions.
• Luster: Vitreous (glassy), especially on fresh crystal faces.
• Transparency: Transparent to translucent depending on inclusions.
• Specific Gravity: 3.0–3.2 g/cm³—moderately dense for a non-metallic mineral.
• Fracture: Subconchoidal to uneven when not cleaved.
• Streak: White.
• Fluorescence: Typically fluoresces blue to violet under UV light due to Eu²⁺ activators.

Transparent purple fluorite crystals from Llamas Quarry, Asturias, Spain.

Occurrences of Purple Fluorite

United States

• Cave-In-Rock District, Hardin County, Illinois: Classic Mississippi Valley-Type (MVT) deposit. Mines include Annabel Lee Mine, Minerva No. 1 Mine, and Rosiclare Mine. Produces large, well-zoned purple cubic crystals. Mn³⁺ and Fe²⁺ variations create visible growth phantoms.
• Elmwood Mine, Smith County, Tennessee: Part of the MVT system. Crystals form in Ordovician dolostone, often associated with calcite and barite.
• Marion County, Kentucky: Shares the Illinois-Kentucky Fluorspar District. Mines such as the Crittenden County Mine and Carrsville Mines have yielded deep purple fluorite, sometimes zoned with blue or green.
• New Mexico (Grant and Socorro Counties): Known sites include the Blanchard Mine and Cookes Peak District, producing collectible purple fluorite with quartz, galena, and barite.

United Kingdom

• Rogerley Mine, Frosterley, County Durham: Unique for daylight fluorescence; uranium-bearing hydrothermal fluids created color centers that emit blue light.
• Weardale, County Durham: Includes Cambokeels Mine, Groverake Mine, and West Pasture Mine. Produces transparent to deeply colored crystals, many fluorescent under UV.
• Derbyshire (Blue John Cavern, Treak Cliff Cavern): “Blue John” fluorite exhibits distinctive blue-purple banding. Historically mined for ornamental stone.

Mexico

• Naica Mine, Chihuahua: Famous for giant gypsum crystals, but also produces fine purple fluorite in limestone-hosted hydrothermal veins.
• Coahuila and Durango: Include the Mapimí (Ojuela) Mine and Melchor Múzquiz Mine, known for attractive fluorite in various hues.

China

• Hunan Province: Major localities include the Xianghualing Mine, Yaogangxian Mine, and Leiping Mine. These produce large, often transparent purple fluorite associated with quartz, cassiterite, and calcite.
• Inner Mongolia (Huanggang Mines): Extensive deposits at Huanggangliang Mine yield deeply colored fluorite, often with blue or green overtones.

Spain

• Asturias (Berbes and La Collada Mines): Northern Spain’s Berbes Mine and La Collada Mine are renowned for sharp, deeply colored purple fluorite crystals often in calcite-rich vugs.

South Africa (Riemvasmaak, Northern Cape): Produces large, octahedral green to purple fluorite crystals.

Germany:

• Black Forest (Wolfsberg and Wölsendorf Districts): Associated with historic silver mining.
• Freiberg District, Saxony: Known for fluorite-barite-silver assemblages.

Switzerland (Alpine clefts): Fluorite crystals occur in high-grade Alpine fissures; often deeply colored, though less common.

Purple fluorite cubes on radiating stilbite matrix. Photo by: Ghulam Mustafa.

Metaphysical and Healing Properties