Botuobinskite
Chemical formula: SrFe²⁺(Ti⁴⁺₁₂Cr³⁺₆)Mg₂[O₃₆(OH)₂]
Botuobinskite is an extremely rare oxide mineral from the crichtonite group, found exclusively in Yakutian diamond deposits.
Properties
- Mohs hardness
- 7.5 - 8
- Color
- Jet black
- Luster
- Metallic
- Streak
- Streak was not measured due to lack of material.
- Density
- 4.3582
- Cleavage
- None
- Fracture
- Irregular/Uneven
- Transparency
- Opaque
- Crystal system
- Trigonal
Diagnostic features
## Identification Identification of botuobinskite is impossible without advanced laboratory techniques. It requires chemical analysis (electron microprobe - EDS/WDS) to confirm its unique composition with a dominance of strontium, iron, titanium, and chromium. X-ray crystallography (XRD) is necessary to confirm its crystal structure. ## Distinguishing from Similar Minerals It can be confused with other black, metallic accessory minerals in kimberlites, such as ilmenite, magnetite, chromite, or other minerals from the crichtonite group (e.g., crichtonite, lindsleyite). Differentiation is based solely on precise chemical composition analysis – botuobinskite is distinguished by its high strontium and chromium content. ## Crystal Forms It forms very small, hexagonal, tabular crystals, often with a hexagonal outline. They occur as single, isolated grains in the host rock.
Geological environment
## Genesis Botuobinskite crystallizes in ultramafic igneous rocks – kimberlites. Its formation is associated with metasomatic processes occurring deep within the Earth's mantle, under conditions of high pressure and temperature. It is a primary mineral that was brought to the surface along with the kimberlite magma. ## Mineral Associations This mineral co-occurs with other minerals typical of kimberlites, such as ilmenite, chromite, pyrope, chromian diopside, and especially with other oxides from the crichtonite group, such as lindsleyite and mathiasite. ## Localities The only confirmed locality of botuobinskite in the world is the Botuobinskaya kimberlite pipe, located within the Nakyn kimberlite field in Yakutia, in the Asian part of Russia.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of a botuobinskite specimen primarily depends on the size and degree of development of its microscopic crystals. The most desirable specimens are those where well-formed, hexagonal crystals are visible, even if they are fractions of a millimeter. Contrast with the lighter host rock (kimberlite) also enhances visual appeal. ## Popular Localities The only source of specimens is the type locality – the Botuobinskaya kimberlite pipe in Yakutia (Russia). Specimens from this location are extremely difficult to acquire and are almost exclusively found in scientific institutions and museums.
Care and storage
## Cleaning Due to the microscopic size of the crystals and their occurrence within the host rock, cleaning individual specimens is practically impossible and not recommended. Any attempts at mechanical or chemical cleaning may irreversibly destroy the mineral. ## What to Avoid Contact with any chemicals, ultrasonic cleaning, and extreme temperature changes should be avoided. Specimens should not be subjected to any hardness tests or other invasive research methods that could damage the delicate crystals. ## Storage Botuobinskite specimens, typically in the form of fragments of the host rock (kimberlite), should be stored under stable conditions, in specialized "micromount" boxes, protected from dust, shocks, and humidity. It is best to store them in darkness to avoid potential degradation due to light.