Tatarskite
Chemical formula: Ca₆Mg₂(S⁶⁺O₄)₂(CO₃)₂(OH)₄Cl₄·7H₂O
Tatarskite is a rare, hydrated calcium and magnesium sulfate, carbonate, hydroxide, and chloride, forming colorless or pale yellow, tabular crystals.
Properties
- Mohs hardness
- 2.5
- Luster
- Vitreous
- Streak
- White
- Density
- 2.341
- Cleavage
- Two sets of distinct pinacoidal cleavages
- Fracture
- Uneven
- Transparency
- Transparent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Characteristic features of tatarskite include its habit (small, tabular crystals, often in radial aggregates), low hardness (2.5 on the Mohs scale), and occurrence in a specific geological environment – marine evaporites. It is transparent, colorless or pale yellow, with a vitreous luster. Final identification requires advanced analytical methods, such as X-ray diffraction (XRD). ## Distinguishing from Similar Minerals It can be confused with other colorless salt minerals found in similar environments, such as halite, sylvite, or some sulfates (e.g., gypsum). It differs from halite and sylvite by its crystal habit (tabular, not cubic) and lack of a salty taste. It differs from gypsum by its habit and harder crystals. Unlike carbonates, it does not react with hydrochloric acid. ## Crystal Forms Tatarskite crystallizes in the orthorhombic system. It forms thin, tabular or bladed crystals, which often arrange into radial or stellate aggregates.
Geological environment
## Genesis Tatarskite is an evaporitic mineral. It forms by precipitation from highly saline waters (brines) within marine evaporite deposits, especially in gypsum-anhydrite caps covering salt diapirs (domes). It is a product of the late stages of diagenesis or weathering of these formations. ## Mineral Associations This mineral co-occurs with other evaporite minerals. It is most commonly found in association with halite, sylvite, gypsum, anhydrite, bischofite, boracite, and other rare borates and sulfates. ## Localities The most important and classic locality for tatarskite is its type locality – the Chelkar salt dome in the West Kazakhstan Region, Kazakhstan. This is the main source of the best-formed specimens of this mineral. Additionally, its presence has been noted in several other salt diapirs worldwide, but these occurrences are of much lesser significance.
Rarity
Very rare
For collectors
## Quality Criteria For collectors, the most desirable specimens are those with well-formed, sharp, transparent crystals that form aesthetic, radial aggregates. Specimens where tatarskite contrasts with the matrix mineral or co-occurs with other rare salt minerals are also highly valued. Due to the small size of the crystals, even small but well-formed clusters are considered valuable. ## Popular Localities The only commercially significant and known source of collectible tatarskite specimens is its type locality: the Chelkar salt dome in Kazakhstan. Specimens from this location are the standard for this mineral species.
Care and storage
## Cleaning Tatarskite specimens should be cleaned with the utmost caution, using only compressed air to remove dust. Due to its softness and potential solubility in water, contact with liquids, including water and alcohol, should be avoided. Mechanical cleaning, even with a soft brush, is risky and can damage delicate crystals. ## What to Avoid Contact with water and other chemicals that could dissolve or damage the mineral must be strictly avoided. Tatarskite is very soft, so it must be protected from scratching by harder minerals. It should also be protected from high temperatures and direct sunlight, which can lead to its dehydration and destruction. ## Storage It is recommended to store tatarskite specimens in stable conditions, in closed, padded "micromount" boxes, to protect them from mechanical damage, dust, and humidity changes. It is best to keep it away from heat sources and in a place with low air humidity.