Uklonskovite
Chemical formula: NaMg(S<sup>6+</sup>O<sub>4</sub>)F·2H<sub>2</sub>O
Uklonskovite is a rare, hydrated sodium and magnesium sulfate, forming colorless, acicular crystals and fibrous aggregates.
Description
## Characteristics Uklonskovite is a mineral from the sulfate group, chemically a hydrated sodium-magnesium sulfate with an additional fluoride anion. It most commonly occurs as fine-grained, felted, or fibrous aggregates. Less frequently, it forms small, well-formed prismatic or acicular crystals, which can create radial groupings. It is a colorless or white mineral with a vitreous luster, which, in the case of fibrous aggregates, transitions to silky. ## Physical Properties This mineral is very soft, with a Mohs hardness of only 2-2.5, meaning it can be scratched with a fingernail. It is also relatively light, with a density of 2.39 g/cm³. It is transparent to translucent. Its key and unusual property is its solubility in water. ## Colors and Varieties Uklonskovite is a mineral with a constant composition and does not form colored varieties. Its only known color is white or colorless. ## History and Name The mineral was first described in 1964 by M.A. Slivko. The name uklonskovite honors Aleksandr Sergeevich Uklonsky (1888-1972), a prominent Russian and Uzbek mineralogist and geochemist, researcher of Central Asian deposits. ## Applications Due to its rarity, small size, and sensitivity to water, uklonskovite has no industrial applications. It is solely an object of scientific and collector interest.
Diagnostic features
## Identification Characteristic features of uklonskovite are its mode of occurrence (fibrous, acicular aggregates), very low hardness (2-2.5), and specific geological environment (gypsum-clay caps over salt domes). A key diagnostic feature is its solubility in water, which is a destructive test and should only be performed on a small fragment. ## Distinguishing from Similar Minerals Uklonskovite can be confused with other white, fibrous sulfates, such as epsomite or hexahydrite, which are also water-soluble and occur in similar environments. Definitive differentiation requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis to confirm the presence of sodium and fluorine. It differs from the much more common gypsum by its significantly greater solubility in water. ## Crystal Forms Crystals are monoclinic, prismatic or acicular. However, they most often form fibrous, radial, felted aggregates or fine-grained masses filling fissures in the host rock.
Geological environment
## Genesis Uklonskovite is a secondary mineral. It forms in the oxidation zones of sulfur deposits, within gypsum-clay caps covering salt domes (diapirs). It is formed by the reaction of sulfate-rich solutions with magnesium and sodium-containing minerals in an arid, desert climate. ## Mineral Associations This mineral occurs in association with other evaporite and sulfate minerals. Most commonly these are: native sulfur, epsomite, hexahydrite, celestine, gypsum, and halite. ## Localities It is a very rare mineral, known from a few localities worldwide. The type locality and main source of the best specimens is the Kushkanatau salt dome in Karakalpakstan, Uzbekistan. It has also been reported in other similar geological formations in Central Asia.
Rarity
Very rare
Collector aspects
## Quality Criteria The collector value of uklonskovite primarily stems from its extreme rarity. Specimens rich in well-formed, acicular or fibrous aggregates are most prized, ideally contrasting with a colorful host rock or co-occurring with other minerals, such as yellow native sulfur. Due to the mineral's fragility, undamaged specimens without signs of dissolution are much more highly valued. ## Popular Localities The only significant source of collector specimens is the type locality – the Kushkanatau salt dome in Uzbekistan. Specimens from other locations are practically unavailable on the market.
Care and storage
## Cleaning Uklonskovite is soluble in water, therefore **it must not be cleaned wet**. The only safe method is dry cleaning using a soft brush or a gentle stream of compressed air to remove dust. ## What to Avoid Avoid all contact with water and other liquids. The mineral is hygroscopic, so it should be protected from high humidity, which can cause its slow degradation. It is also very soft and brittle, susceptible to mechanical damage. It should be protected from high temperatures, which can lead to the loss of crystallization water. ## Storage Uklonskovite specimens should be stored in dry conditions. The best solution is a tightly sealed container (e.g., a "membrane box") or a display case with a desiccant (e.g., silica gel). It should be kept away from heat sources and direct sunlight.