Parafransoletite
Chemical formula: Ca₃Be₂(PO₄)₂(PO₃OH)₂·4H₂O
Parafransoletite is a rare hydrated calcium beryllium phosphate, forming small, colorless or white crystals in radial aggregates.
Properties
- Mohs hardness
- 2.5
- Color
- Colorless, white
- Luster
- Vitreous
- Streak
- White
- Density
- 2.54
- Cleavage
- Perfect on {010}
- Fracture
- Uneven
- Transparency
- Transparent,Translucent
- Crystal system
- Triclinic
Diagnostic features
## Identification A characteristic feature of parafransoletite is its forms of occurrence – radial aggregates composed of small, acicular or bladed crystals. White color, vitreous luster, and occurrence in granitic pegmatites are key indicators. ## Distinguishing from similar minerals Parafransoletite is visually almost identical to fransoletite. A definitive distinction between these two minerals is possible almost exclusively by advanced analytical methods, such as X-ray diffraction (XRD), which allows for the determination of the crystallographic system (monoclinic for parafransoletite, orthorhombic for fransoletite). It can also be confused with other white, acicular phosphates from pegmatites, e.g., wardite or strengite in certain forms. ## Crystal forms Crystals are elongated and flattened, with a bladed or acicular habit. They typically form radial, spherical or hemispherical aggregates and rosettes.
Geological environment
## Genesis Parafransoletite is a secondary mineral, formed in the late stages of crystallization of complex granitic pegmatites. It forms as a result of hydrothermal processes acting on primary phosphates, such as triplite, in the presence of beryllium-rich solutions. ## Mineral associations This mineral co-occurs with other pegmatitic phosphates. At the type locality (Tip Top mine, USA), it was found in association with montgomeryite, tiptopite, roscherite, englishite, as well as quartz, microcline, and muscovite. In Brazil, it is accompanied by, among others, eosphorite and zanazziite. ## Localities The most important and well-documented occurrences of parafransoletite worldwide are: - **USA**: Tip Top mine in Custer County, South Dakota (type locality). - **Brazil**: Gentil Pegmatite in Mendes Pimentel, Minas Gerais.
Rarity
Very rare
For collectors
## Quality criteria The most prized parafransoletite specimens are those with well-formed, spherical aggregates of a distinctly radial structure, contrastingly set on a rock matrix. The size of the aggregates is crucial – the larger the diameter of the "ball," the more valuable the specimen. The aesthetic composition and lack of damage to the delicate crystals are also important. ## Popular localities By far the most known and valued specimens come from the type locality – the Tip Top mine in South Dakota, USA. Specimens from this location are considered the global standard for this mineral.
Care and storage
## Cleaning Specimens should be cleaned only very carefully, using a soft brush to remove dust. Due to the fragility and delicacy of the acicular crystals, wet cleaning or the use of ultrasonic cleaners is not recommended. ## What to avoid Avoid contact with chemicals, especially acids, which can damage the mineral. Aggregates are very brittle and susceptible to mechanical damage – even a stronger touch can destroy the delicate crystals. Protect it from high temperatures, which can lead to dehydration. ## Storage It is recommended to store specimens in closed "micromount" boxes, which protect them from dust, shocks, and mechanical damage. Do not expose it to direct sunlight.