Pertsevite-(F)
Chemical formula: Mg<sub>2</sub>BO<sub>3</sub>F
Pertsevite-(F) is a rare magnesium borate, forming colorless to white, granular aggregates in magnesian skarns.
Properties
- Mohs hardness
- 5
- Luster
- Vitreous
- Streak
- White
- Density
- 2.93 - 2.97
- Cleavage
- Good on {010}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Identifying pertsevite-(F) in the field is practically impossible. It requires advanced analytical methods, such as X-ray diffraction (XRD) and chemical analysis (e.g., electron microprobe) to confirm its composition and structure. Visually, it is a colorless to white mineral with a vitreous luster, occurring as fine grains in skarns. ## Distinguishing from Similar Minerals It can be confused with other colorless minerals found in skarns, such as kotoite, fluoborite, sapphirine, or chondrodite. Distinguishing it from these requires specialized laboratory tests. Pertsevite-(F) is the fluorine analogue of pertsevite-(OH). ## Crystal Forms It most often forms irregular, rounded grains and granular aggregates. Poorly formed, thick tabular crystals are rarely encountered.
Geological environment
## Genesis Pertsevite-(F) is a metamorphic mineral, formed under high-temperature conditions in magnesian skarns. It forms as a result of contact metasomatism at the interface of granitoid intrusions with dolomites or magnesite rocks, in a boron- and fluorine-rich environment. ## Mineral Associations This mineral coexists with other borates and skarn minerals, such as kotoite, ludwigite, fluoborite, sapphirine, sinhalite, chondrodite, spinel, calcite, dolomite, and forsterite. ## Localities The most important and well-documented localities of pertsevite-(F) worldwide include: - W.C. Clark Mine (Commercial Mine), Crestmore, Riverside County, California, USA (type locality). - Nalednoye iron-boron deposit, Tas-Khayakhtakh Mountains, Yakutia, Russia. - Lyudmila Mine, Tazheran (Tazheranskaya) area, Irkutsk Oblast, Russia.
Rarity
Very rare
For collectors
## Quality Criteria The quality of pertsevite-(F) specimens is assessed primarily from a scientific, rather than aesthetic, perspective. The most valuable samples are those with well-identified, rich grain aggregates, preferably with visible (though rare) crystalline forms. Accurate analysis confirming the mineral's identity and the presence of rare associated minerals is crucial. ## Popular Localities Specimens from the type locality in California and from deposits in Yakutia, Russia, are most highly valued by specialized scientific and systematic collections.
Care and storage
## Cleaning It is recommended to clean only with a soft, dry brush to remove dust. Avoid water and all chemical agents, as its reaction to them is unknown, and as a borate, it may be sensitive to moisture. ## What to Avoid Avoid contact with acids and other chemicals. The mineral should be protected from moisture, high temperatures, and ultrasound. Due to the lack of data on its stability, extreme caution should be exercised. ## Storage Pertsevite-(F) specimens are best stored in stable conditions, in a closed display box, away from dust, moisture, and direct sunlight. Due to its occurrence as small grains, often in the host rock, the specimen should be protected from impacts and abrasions.