Fluorcaphite
Chemical formula: SrCaCa<sub>3</sub>(PO<sub>4</sub>)<sub>3</sub>F
Fluorcaphite is a rare mineral from the apatite group, a strontium and calcium phosphate, distinguished by its hexagonal crystals.
Properties
- Mohs hardness
- 5
- Luster
- Vitreous
- Streak
- White
- Density
- 3.28 - 3.51
- Cleavage
- Indistinct on {0001}
- Fracture
- Uneven, Conchoidal
- Transparency
- Transparent to Translucent
- Crystal system
- Hexagonal
Diagnostic features
## Identification Fluorcaphite is identified by its characteristic crystal form – hexagonal, elongated prisms. Its hardness (5 on the Mohs scale), vitreous luster, and occurrence in a specific geological environment (alkaline pegmatites) are key diagnostic features. Due to the small size of the crystals, final identification often requires advanced analytical methods, such as EDS analysis. ## Differentiation from Similar Minerals Fluorcaphite can be confused with other minerals from the apatite group, such as fluorapatite or hydroxyapatite. Distinguishing it from these minerals based on visual characteristics is practically impossible and requires chemical analysis to determine the dominance of strontium in a specific structural position. It also differs from them by a slightly higher density. ## Crystal Forms Fluorcaphite crystals have a prismatic habit, are elongated along the crystallographic c-axis, and terminated by flat faces. They form hexagonal columns. They occur as single, well-formed crystals or in granular aggregates.
Geological environment
## Genesis Fluorcaphite forms under hydrothermal conditions within nepheline syenite pegmatites, which are highly differentiated and rich in rare elements. It is a mineral of the late stage of crystallization in these environments. ## Mineral Associations This mineral co-occurs with other rare alkaline minerals. In the type locality (Khibiny Massif), it was found in association with natrolite, lorenzenite, eudialyte, lomonosovite, aegirine, microcline, nepheline, sodalite, and other minerals from the apatite group. ## Localities The most important and well-documented fluorcaphite localities in the world are in Russia, in the ultra-alkaline massifs of the Kola Peninsula. The type locality is Mount Koashva in the Khibiny Massif. It is also known from the Lovozero Massif.
Rarity
Very rare
For collectors
## Quality Criteria The most prized specimens by collectors are those with well-formed, sharp, and transparent crystals that are clearly visible on the rock matrix. Color contrast with associated minerals, such as white natrolite, also enhances the specimen's appeal. Due to the mineral's rarity, even microscopic but well-formed crystals are considered valuable. ## Popular Localities By far the most sought-after fluorcaphite specimens come from its type locality – Mount Koashva in the Khibiny Massif on the Kola Peninsula in Russia. This is practically the only source of specimens of collector significance.
Care and storage
## Cleaning Fluorcaphite specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, distilled water can be used, but prolonged soaking should be avoided. Always dry the specimen thoroughly after cleaning. ## What to Avoid This mineral is sensitive to strong acids, which can damage it. Ultrasonic cleaners and steam cleaning should be avoided. It should also be protected from sudden temperature changes and direct, prolonged exposure to sunlight. ## Storage It is recommended to store fluorcaphite in separate, padded collector boxes to prevent scratches from harder minerals. It should be protected from dust and moisture. Due to its brittleness, specimens should be displayed in stable showcases, away from areas prone to shocks.