Arctite
Chemical formula: (Na<sub>5</sub>Ca)Ca<sub>6</sub>Ba(PO<sub>4</sub>)<sub>6</sub>F<sub>3</sub>
Arktite is a rare, colorless or white sodium, calcium, and barium phosphate, forming characteristic tabular crystals with a hexagonal outline.
Properties
- Mohs hardness
- 5
- Luster
- Vitreous
- Streak
- White
- Density
- 3.55
- Cleavage
- Imperfect on {0001}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Trigonal
Diagnostic features
## Identification Arktite can be identified by its characteristic crystal habit – thick, hexagonal tablets, often grouped in aggregates. Its vitreous luster, colorless or white color, and hardness of 5 on the Mohs scale are also important diagnostic features. Its occurrence in a specific geological environment (alkaline massifs) is a key indicator. ## Distinguishing from Similar Minerals Arktite can be confused with other colorless minerals with a hexagonal habit, such as apatite, calcite, or some zeolites. It differs from apatite by a slightly different habit (more tabular than prismatic) and specific parageneses. It is much harder than calcite and does not react with hydrochloric acid. Unlike many zeolites, arktite has a higher density. ## Crystal Forms Arktite crystals are trigonal but exhibit pseudohexagonal symmetry. They most often form thick, tabular crystals with a hexagonal outline. They also occur as short prisms. They frequently form radial or parallel clusters and aggregates.
Geological environment
## Genesis Arktite is a hydrothermal mineral associated with differentiated alkaline massifs and their pegmatites. It forms in the late stages of crystallization, in veins cutting rocks such as urtites and foyaite. It is a characteristic mineral of ultrabasic alkaline rock complexes. ## Mineral Associations This mineral co-occurs with a wide range of other rare alkaline minerals. Its most common associations include natrosilite, rasvumite, lomonosovite, villiaumite, thermonatrite, ewaldite, belovite-(Ce), aegirine, natrite, and umbite. ## Localities The most important and classic arktite localities are in Russia, on the Kola Peninsula, in the Khibiny and Koashva alkaline massifs. These are the sources of the world's best specimens of this mineral. Outside of Russia, its occurrence has also been reported in the Mont Saint-Hilaire alkaline complex in Quebec, Canada, which is known for many rare minerals.
Rarity
Rare
For collectors
## Quality Criteria The most prized arktite specimens by collectors are those consisting of sharp, well-formed, transparent, and colorless crystals. Large, single crystals with a distinct hexagonal outline and vitreous luster are particularly sought after. The aesthetic appeal of a specimen is also enhanced by attractive compositions with other rare minerals, such as belovite-(Ce) or rasvumite. ## Popular Localities By far the best and most desirable arktite specimens come from the Khibiny Massif on the Kola Peninsula in Russia. This locality has yielded the largest and best-formed crystals of this mineral. Specimens from Mont Saint-Hilaire in Canada are much rarer and generally smaller.
Care and storage
## Cleaning Arktite 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 thoroughly dry the specimen after wet cleaning. ## What to Avoid Arktite is sensitive to acids, which can damage it. Contact with household and laboratory chemicals should be avoided. It should also not be heated or subjected to sudden temperature changes. Due to its moderate hardness, it should be protected from scratching by harder minerals (e.g., quartz). ## Storage Arktite specimens are best stored in separate, padded boxes or display cases to prevent abrasions and mechanical damage. It should be protected from dust and direct, prolonged exposure to sunlight, although this is not considered particularly harmful.