Nacaphite
Chemical formula: Na<sub>2</sub>Ca(PO<sub>4</sub>)F
Nakafite is a rare sodium calcium phosphate, forming colorless or white, tabular crystals and spherulitic aggregates.
Properties
- Mohs hardness
- 4
- Luster
- Vitreous, Pearly
- Streak
- White
- Density
- 2.82
- Cleavage
- Perfect on {010}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Nakafite can be identified by its characteristic spherulitic or radial aggregates composed of small, tabular crystals. Key features include its white or colorless appearance, pearly luster on cleavage surfaces, and perfect unidirectional cleavage. Its occurrence in pegmatites within alkaline massifs is also an important indicator. ## Distinguishing from Similar Minerals It can be confused with other white phosphate minerals or silicates found in similar environments, such as some zeolites (e.g., natrolite) or pectolite. It differs from natrolite in crystal habit (tabular instead of acicular) and lower hardness. It is distinguished from pectolite by its lower hardness and perfect cleavage. However, definitive confirmation requires advanced analytical methods (XRD, EDS). ## Crystal Forms Crystals are most often tabular or bladed, flattened parallel to the direction of perfect cleavage. They usually form radial, spherulitic, or fan-shaped aggregates. Less commonly, they occur as single, well-formed crystals.
Geological environment
## Genesis Nakafite is a hydrothermal mineral associated with alkaline rocks. It forms in the late stages of crystallization in nepheline syenite pegmatites, where it fills voids and fractures. It forms in an environment rich in sodium, calcium, and phosphorus. ## Mineral Associations This mineral co-occurs with other minerals typical of alkaline pegmatites. The most common associations include aegirine, nepheline, microcline, lorenzenite, eudialyte, lomonosovite, natrolite, analcime, cancrinite, thermonatrite, and villiaumite. ## Localities The most important and well-documented occurrences of nakafite worldwide are in Russia, within the alkaline massifs of the Kola Peninsula. These are primarily the Khibiny Massif (Mount Rasvumchorr, Koashva, Yukspor) and the Lovozero Massif (Mount Alluaiv). Outside Russia, occurrences have been reported in the Ilimaussaq alkaline complex in Greenland.
Rarity
Rare
For collectors
## Quality Criteria The most prized specimens by collectors are those with well-formed, sharp spherulites or radial aggregates with a distinct pearly luster. A contrasting placement on a dark rock matrix, for example on aegirine, significantly enhances the visual appeal of the specimen. The size of the aggregates is also important – the larger and more complete, the higher the value. Purity (lack of mechanical damage) is crucial due to the mineral's brittleness. ## Popular Localities Undoubtedly, the best and most sought-after nakafite specimens come from the Khibiny Massif on the Kola Peninsula in Russia, which is its type locality. Specimens from Mount Koashva are considered classic for this mineral.
Care and storage
## Cleaning It is recommended to clean only with compressed air to remove dust. Due to its perfect cleavage, mechanical cleaning, including brushes, should be avoided. Contact with water, especially acids, can damage the mineral's surface. ## What to Avoid Avoid contact with all chemicals, especially acids. The mineral is relatively soft and brittle, so it must be protected from impacts and scratches. It should not be heated or subjected to ultrasound. ## Storage Nakafite specimens should be stored in separate, padded display boxes to prevent mechanical damage and contact with harder minerals. They should be protected from dust and moisture.