Ekaterinite

Chemical formula: Ca<sub>2</sub>B<sub>4</sub>O<sub>7</sub>Cl<sub>2</sub>·2H<sub>2</sub>O

Ekaterinite is a very rare hydrated calcium borate with chlorine, forming colorless, tabular crystals in salt deposits.

## Characteristics Ekaterinite is a borate group mineral, chemically classified as a hydrated calcium borate with chlorine. It occurs as small, thin, tabular crystals with a hexagonal outline. These crystals rarely occur individually, more often forming fan-shaped aggregates, rosettes, or fine-grained, felted masses. It is colorless to white, which, combined with the small size of the crystals, makes it not a visually spectacular mineral. ## Physical Properties This mineral is relatively soft, with a hardness of about 2.5 on the Mohs scale. It is characterized by a vitreous luster on crystal faces and a pearly luster on cleavage planes. It is transparent to translucent. Its density is approximately 2.42 g/cm³. A special feature is its solubility in water. ## Colors and Varieties Ekaterinite is typically colorless or white. No colored varieties or trade names are distinguished. ## History and Name The mineral was first described in 1979 by a group of Russian mineralogists (S. V. Malinko, D. P. Shashkin, K. V. Yurkina, I. V. Zaytseva). Its name comes from the city of Yekaterinburg (formerly Sverdlovsk) in Russia, an important scientific and industrial center in the Urals. ## Uses Due to its extreme rarity and small size, ekaterinite has no industrial application. It is solely an object of scientific interest and is valued in advanced systematic collections.

Properties

Mohs hardness
2.5
Luster
Vitreous, Pearly
Streak
White
Density
2.42
Cleavage
Perfect on {0001}
Fracture
Uneven
Transparency
Transparent to Translucent
Crystal system
Hexagonal

Diagnostic features

## Identification Key diagnostic features of ekaterinite are its habit in the form of thin, hexagonal tablets, perfect cleavage in one direction (basal plane), low hardness, and pearly luster on cleavage surfaces. The most important test, however, is its solubility in water. Occurrence in paragenesis with salt minerals is also a strong indication. ## Distinguishing from Similar Minerals Ekaterinite can be confused with other colorless, tabular minerals, such as brucite or some micas. Brucite also has a hexagonal habit and perfect cleavage but is insoluble in water. Micas (e.g., muscovite) are much more elastic. Final differentiation from other rare borates often requires advanced analytical methods. ## Crystal Forms Ekaterinite crystallizes in the form of thin, hexagonal plates and tablets. These crystals often arrange themselves into fan-shaped or radial aggregates, and also form rosettes. It is also found in felted or fine-grained masses.

Geological environment

## Genesis Ekaterinite is a mineral of metasomatic origin. It forms under specific conditions within boron skarns, which develop at the contact of magmatic intrusions with sedimentary rocks rich in evaporites (salt deposits). ## Mineral Associations This mineral occurs in association with other borate minerals and evaporites. Its typical associations are shabynite, hydrochlorborite, halite, sylvite, and carnallite. ## Localities Ekaterinite is an extremely rare mineral, known practically from only one place in the world. This is its type locality – the Korshunovskoye iron deposit (Korshunovskiy GoK) in the Irkutsk Oblast, Siberia, Russia.

Rarity

Very rare

For collectors

## Quality Criteria In the case of such a rare mineral as ekaterinite, the main criterion of value is its mere presence and certain identification. The most desirable specimens are those with well-formed, even if small, crystals in the form of hexagonal tablets or their clear aggregates (rosettes). Additional value is provided by co-occurrence with other rare minerals from the same locality. The size and transparency of the crystals are secondary factors compared to the quality of the crystal form. ## Popular Localities The only source of collectible ekaterinite specimens is its discovery site – the Korshunovskoye deposit in Siberia, Russia. Practically all samples available worldwide come from this single locality.

Care and storage

## Cleaning Ekaterinite is soluble in water, so **it must not be cleaned wet**. Contact with water, even a damp cloth, can permanently damage or destroy the specimen. To remove dust, use only a soft, dry brush or compressed air from a safe distance. ## What to Avoid Avoid contact with water, all liquids and chemicals, and storage in conditions of high humidity. The mineral is very soft (hardness 2.5) and brittle, susceptible to scratches and mechanical damage. Protect it from impacts and contact with harder minerals. ## Storage Ekaterinite specimens are best stored in a dry place, in a closed, airtight container (e.g., a "perky box"), to protect them from moisture and dust. Display should be away from sources of moisture and in a place where the specimen will not be exposed to shocks or touching.

Sources

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