Ferrotaaffeite-6<i>N</i>'3<i>S</i>
Chemical formula: BeFe<sup>2+</sup><sub>2</sub>Al<sub>6</sub>O<sub>12</sub>
Ferrotaaffeite-6N'3S is an extremely rare mineral from the taaffeite group, characterized by iron dominance, found in metamorphic rocks.
Properties
- Mohs hardness
- 7.5
- Luster
- Vitreous
- Streak
- Brown
- Density
- 4.10
- Cleavage
- Imperfect on {0001}
- Fracture
- Conchoidal
- Transparency
- Transparent
- Crystal system
- Hexagonal
Diagnostic features
## Identification Identification of ferrotaaffeite-6N'3S is impossible without advanced laboratory techniques. It requires chemical analysis (e.g., using an electron microprobe - EDS/WDS) to confirm the iron-dominant composition over magnesium, and X-ray diffraction (XRD) to determine the crystal structure. Visually, it is a small, dark brown to black, hexagonal grain intergrown in the rock. ## Distinguishing from Similar Minerals It can be confused with other minerals from the taaffeite group, especially magnesiotaaffeite, from which it is visually indistinguishable. The difference can only be determined by chemical analysis. It may also be confused with other dark minerals found in skarns, such as magnetite, hercynite, or pleonaste, but it differs from them in crystal form and hardness. ## Crystal Forms It forms small, hexagonal, tabular crystals, often with a hexagonal outline. They occur as single grains intergrown with other minerals.
Geological environment
## Genesis Ferrotaaffeite-6N'3S forms under conditions of high-temperature contact metamorphism. It has been found in magnesian skarns that formed at the contact of syenite intrusions with dolomites. It is a product of metasomatic reactions occurring under these specific geological conditions. ## Mineral Associations At the type locality (Tayozhnoye mine), ferrotaaffeite-6N'3S coexists with minerals such as phlogopite, magnetite, spinel (pleonaste), forsterite, enstatite, högbomite, clinohumite, geikielite, ilmenite, graphite, calcite, dolomite, baddeleyite, and hydrotalcite. ## Localities The only confirmed occurrence of this mineral in the world is its type locality: the Tayozhnoye mine, located in the Aldan Mountains on the Aldan Plateau, in the Sakha Republic (Yakutia), Russia.
Rarity
Extremely rare
For collectors
## Quality Criteria As a microscopic mineral of purely scientific and systematic value, it is not subject to standard quality assessment criteria applied to macroscopic specimens. The most valuable samples are those where ferrotaaffeite-6N'3S crystals are as large as possible, well-formed, and identified by chemical analysis. The presence of rare associated minerals is also crucial. ## Popular Localities The only source of specimens is the Tayozhnoye mine in Russia. Material from this locality is extremely difficult to acquire and appears on the collector's market sporadically, mainly among specialized collectors of rare minerals and "micromounts."
Care and storage
## Cleaning Due to the extreme rarity and microscopic size of the crystals, which are typically intergrown in the rock matrix, mechanical cleaning is neither recommended nor practiced. Specimens should be left in their undisturbed state. ## What to Avoid Contact with strong acids and chemicals should be avoided. Despite its high hardness, specimens should be protected from impacts and abrasion, which could damage the microscopic crystals. ## Storage Specimens containing ferrotaaffeite-6N'3S should be stored under stable conditions, in specialized "micromount" boxes, protecting them from dust, moisture, and mechanical damage. It is best to store them in darkness to avoid potential (though unstudied) effects of light.