Yarzhemskiite

Chemical formula: K[B<sub>5</sub>O<sub>7</sub>(OH)<sub>2</sub>]·H<sub>2</sub>O

Yarzhemskiite is a rare borate mineral, forming colorless or white, tabular crystals and radial aggregates.

## Characteristics Yarzhemskiite is a hydrated potassium borate. It occurs as small, colorless to white, tabular or platy crystals, which often form radial or fibrous aggregates. Crystals are typically very small, reaching up to 2 mm in length. ## Physical Properties This mineral is characterized by a hardness of approximately 2.5 on the Mohs scale. It has a vitreous luster. It is transparent to translucent. The calculated density is 2.16 g/cm³. ## History and Name The mineral's name honors Pyotr Yakovlevich Yarzhemsky (1885-1956), a Russian geologist and researcher of potash salt deposits. It was approved as a new mineral by the IMA in 1961. The type locality is the Inder potash salt deposit in Atyrau, Kazakhstan.

Properties

Mohs hardness
2.5
Luster
Vitreous
Streak
White
Density
2.16
Cleavage
Good on {010}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Yarzhemskiite is identified by its characteristic radial aggregates composed of small, platy crystals. Its occurrence in evaporitic potash salt deposits is a key indicator. Low hardness and white color are also auxiliary features. ## Distinguishing from Similar Minerals It can be confused with other borates found in similar environments, such as ulexite or colemanite. Ulexite forms characteristic fibrous aggregates with a silky luster, often exhibiting the "television stone" effect, which is not observed in yarzhemskiite. Other borates often have different crystal forms or higher hardness. ## Crystal Forms Crystals are tabular or platy, elongated along one axis. They most often form radial, stellate, or fibrous aggregates, as well as granular masses.

Geological environment

## Genesis Yarzhemskiite is an evaporitic mineral. It forms in marine potassium-magnesium salt deposits, within gypsum-anhydrite caps covering salt domes. It forms as a result of hydrothermal or metasomatic processes occurring within these deposits. ## Mineral Associations This mineral co-occurs with other borates and salt minerals, such as inderborite, hydroboracite, gypsum, anhydrite, halite, and sylvite. ## Localities The most important and type locality for yarzhemskiite is the Inder Lake region in the Atyrau Oblast, Kazakhstan. This is the only confirmed and well-documented locality for this mineral in the world.

Rarity

Very rare

For collectors

## Quality Criteria The most prized yarzhemskiite specimens are those that exhibit well-formed, radial aggregates with a distinct structure. The size of the aggregates and contrast with the matrix (e.g., darker clay rock) enhance their attractiveness. Due to its rarity, any well-formed specimen is valuable to collectors specializing in rare minerals or borates. ## Popular Localities The only source of collector specimens is the Inder boron deposit in Kazakhstan.

Care and storage

## Cleaning Due to its low hardness and potential water solubility, cleaning should be limited to an absolute minimum. If necessary, compressed air can be used to remove dust, or it can be very carefully wiped with a soft, dry brush. ## What to Avoid Contact with water and other liquids that may dissolve or damage the mineral should be strictly avoided. It should be protected from high temperatures, humidity, and chemicals. This is a very brittle mineral and sensitive to mechanical damage. ## Storage Yarzhemskiite specimens are best stored in tightly sealed containers (so-called "perky boxes") or in display cases with controlled, low air humidity. Exposure to direct sunlight and temperature changes should be avoided.

Sources

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