Sinkankasite
Chemical formula: Mn<sup>2+</sup>Al(PO<sub>3</sub>OH)<sub>2</sub>(OH)·6H<sub>2</sub>O
Sinkankasite is a very rare, hydrated manganese aluminum phosphate, forming colorless, acicular crystals in granitic pegmatites.
Properties
- Mohs hardness
- 4
- Luster
- Vitreous
- Streak
- White
- Density
- 2.33
- Cleavage
- Perfect on {010}
- Transparency
- Transparent
- Crystal system
- Triclinic
Diagnostic features
## Identification Key to the identification of sinkankasite are its characteristic, colorless, acicular crystals forming radial aggregates. Identification is confirmed by its occurrence in paragenesis with other rare phosphates in granitic pegmatites. ## Distinguishing from Similar Minerals It can be confused with other colorless, acicular secondary minerals, such as wavellite or some zeolites. Differentiation usually requires advanced research methods (e.g., XRD), although analysis of associated minerals and knowledge of the locality are helpful. ## Crystal Forms It forms slender, acicular to fibrous crystals, elongated along the [001] axis and often striated. These crystals combine into fan-shaped, radial, or chaotic aggregates, and also form crusts on other minerals.
Geological environment
## Genesis Sinkankasite is a secondary phosphate mineral, formed in low-temperature hydrothermal zones. It forms in complex granitic pegmatites as a result of the alteration of primary phosphates, such as triphylite. ## Mineral Associations It co-occurs with other phosphates, such as hureaulite, strengite, rockbridgeite, frondelite, laueite, jahnsite-(CaMnMn), vivianite, as well as triphylite and zwieselite. ## Localities This is an extremely rare mineral. The most important and also the type locality for its occurrence is the Barker-Ferguson mine in Pennington County, South Dakota, USA. Beyond this locality, it has only been reported in a few other places worldwide, including Brazil.
Rarity
Very rare
For collectors
## Quality Criteria The collector's value of sinkankasite is primarily determined by its rarity. Specimens with well-formed, radial aggregates on the matrix are most prized. Association with other rare phosphates is also important. The size and aesthetics of the aggregates, even though the crystals are small and colorless, significantly enhance the attractiveness of the specimen. ## Popular Localities Almost all specimens available on the collector's market come from the type locality - the Barker-Ferguson mine in the Keystone area, South Dakota, USA. Specimens from this location are the standard for the species.
Care and storage
## Cleaning Specimens should be cleaned very carefully. Only gentle rinsing in distilled water is permissible. Ultrasonic cleaners and mechanical cleaning, e.g., with brushes, which can damage fragile crystals, should be avoided. ## What to Avoid The mineral is sensitive to high temperatures, which can lead to its dehydration and destruction of its structure. Contact with acids and other chemicals should be avoided. Due to its low hardness and perfect cleavage, it is very susceptible to mechanical damage. ## Storage It is recommended to store specimens in separate, padded boxes to protect them from shocks and abrasions. They should be kept in stable conditions, away from direct sunlight and heat sources.