Aleksandrovite

Chemical formula: KCa₇Sn₄+₂Li₃Si₁₂O₃₆F₂

A very rare mineral from the silicate group, containing tin and lithium, known exclusively from one locality in the world in the form of colorless, prismatic crystals.

## Characteristics Aleksandrovite is an extremely rare, complex silicate from the britholite group, with a unique chemical composition containing potassium, calcium, tin, lithium, and fluorine. It forms colorless, transparent, prismatic crystals that can reach up to 5 mm in length. They usually occur as small, radial or subparallel aggregates intergrown with other minerals. ## Physical Properties This mineral is characterized by a vitreous luster and is fully transparent. Its Mohs hardness is approximately 5, and its density is 3.06 g/cm³. It exhibits perfect cleavage in one direction. ## Colors and Varieties Aleksandrovite is colorless. No colored varieties or trade names are known. ## History and Name The mineral was described in 2007 by a team of mineralogists led by Igor V. Pekov. Its name honors Stanislav Mikhailovich Aleksandrov (1931–2005), a Russian geochemist and mineralogist from the V.I. Vernadsky Institute of Geochemistry and Analytical Chemistry in Moscow, for his contribution to the study of tin-bearing and boron-bearing skarns. ## Uses Due to its extreme rarity, aleksandrovite has no industrial applications. It is solely an object of scientific interest and a valuable acquisition for specialized collectors of rare minerals.

Properties

Mohs hardness: 5
Luster: Vitreous
Streak: White
Density: 3.06
Cleavage: Perfect on {001}
Fracture: Uneven
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification The key diagnostic feature of aleksandrovite is its locality – this mineral is known only from one place in the world. In collecting conditions, it is recognized by its colorless, prismatic crystals with a vitreous luster, occurring in a characteristic paragenesis. Final identification requires advanced analytical methods, such as X-ray diffraction (XRD) and chemical composition analysis (EDS). ## Distinguishing from Similar Minerals Aleksandrovite can be confused with other colorless minerals found in skarns, such as quartz, danburite, or some feldspars. It is distinguished from them by its perfect cleavage, higher density, and unique chemical composition, particularly the presence of tin and lithium, which cannot be determined without specialized equipment. ## Crystal Forms The crystals are elongated, prismatic, often terminated by simple faces. They usually form small, radial or chaotically oriented aggregates intergrown in the host rock.

Geological environment

## Genesis Aleksandrovite forms under specific conditions within calcareous skarns. Its occurrence is associated with metasomatic processes at the contact of granitoid intrusions with carbonate rocks, in an environment rich in fluorine, tin, and boron. ## Mineral Associations This mineral co-occurs with fluorite, calcite, vesuvianite, andradite, wollastonite, danburite, grigorievite, and other tin-bearing silicates and oxides. ## Localities The only confirmed locality of aleksandrovite in the world is the Verkhnee tin and boron deposit in the Verkhoyansk district, Sakha Republic (Yakutia), Russia. This is its type locality.

Rarity

Extremely rare

For collectors

## Quality Criteria In the case of such a rare mineral, any specimen with well-formed, undamaged, and transparent crystals is considered exceptionally valuable. The value of a specimen increases if the aleksandrovite crystals are well-exposed on the rock matrix and are accompanied by other rare minerals from that locality. The size of the crystals and aggregates is also a key factor. ## Popular Localities All known and available specimens on the collector's market come from a single location – the Verkhnee deposit in Yakutia (Russia). This is the sole source of this mineral.

Care and storage

## Cleaning Aleksandrovite specimens should be cleaned with the utmost care, preferably using compressed air to remove dust. If necessary, a soft brush and distilled water can be used, immediately drying the specimen. Due to its rarity, any mechanical interventions are discouraged. ## What to Avoid Ultrasonic cleaners, strong chemicals, acids, and solvents should be strictly avoided. The mineral should be protected from sudden temperature changes and prolonged exposure to direct sunlight. ## Storage It is recommended to store specimens in stable conditions, in sealed "micromount" boxes that protect against dust, moisture, and mechanical damage. Each specimen should be properly labeled, taking into account its unique origin.

Sources

IMA Mineral List (CNMNC)