Fedorovskite

Chemical formula: Ca<sub>2</sub>Mg<sub>2</sub>B<sub>4</sub>O<sub>7</sub>(OH)<sub>6</sub>

Fedorovskite is a rare hydrated calcium and magnesium borate, forming colorless, acicular crystals and radial aggregates.

## Characteristics Fedorovskite is a mineral from the borate group, chemically classified as a hydrated calcium and magnesium borate. It occurs as fine, acicular or bladed crystals, which often form radial or tangled aggregates. Individual crystals are typically colorless and transparent, and their small size causes the mineral to appear white with a silky luster in aggregates. ## Physical Properties The mineral is characterized by a hardness of approximately 4.5 on the Mohs scale. Its crystals exhibit a vitreous luster, which transitions to silky in fine-grained aggregates. It is a light mineral, with a density of 2.46 g/cm³. Crystals are transparent, but in aggregate form, they become translucent to opaque. ## Colors and Varieties Fedorovskite is usually colorless or white. No colored or commercial varieties have been identified. ## History and Name The mineral was first described in 1976 by S.V. Malinko, I.V. Petrova, and G.S. Rumyantseva. Its name honors Evgraf Stepanovich Fedorov (1853-1919), a prominent Russian crystallographer, mineralogist, and mathematician, who laid the foundations of modern structural crystallography. ## Applications Fedorovskite has no industrial significance and is solely an object of interest for collectors and a subject of scientific research.

Properties

Mohs hardness
4.5
Luster
Vitreous
Streak
White
Density
2.46
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Characteristic features of fedorovskite include its forms of occurrence – radial or tangled aggregates composed of very fine, acicular or bladed crystals. Its white color, silky luster in aggregates, and relatively low hardness aid in identification. This mineral occurs in the specific environment of skarn rocks. ## Distinguishing from Similar Minerals Fedorovskite can be confused with other fibrous borates or zeolites. It is distinguished from zeolites by its higher hardness and specific occurrence environment (skarns). From other borates, such as ulexite, it can be distinguished by its harder crystals and the absence of the characteristic "TV stone" effect of ulexite. However, precise identification requires advanced research methods, such as X-ray diffraction (XRD). ## Crystal Forms Crystals are elongated, acicular or bladed, showing a tendency to form radial, stellate, or haphazardly tangled aggregates. Single, well-formed crystals are observed less frequently.

Geological environment

## Genesis Fedorovskite is a hydrothermal mineral, forming in magnesian skarns. It forms as a result of metasomatic interaction of boron-rich solutions with carbonate rocks (dolomites) in contact zones with magmatic intrusions. ## Mineral Associations This mineral coexists with other borates and skarn minerals. Its most common associations include calcite, dolomite, kotoite, ludwigite, szaibelyite (ascharite), magnetite, and minerals from the serpentine group. ## Localities The most important and also the type locality (località typica) for fedorovskite is the Solongo boron deposit in Buryatia (Russia). This is the main and practically only known worldwide locality from which well-documented specimens of this mineral originate.

Rarity

Very rare

For collectors

## Quality Criteria The most valued specimens by collectors are those with clearly formed, radial aggregates of acicular crystals, creating aesthetic "suns" or "stars" on the rock matrix. The size and completeness of these aggregates, as well as the contrast with surrounding minerals, are important. Purity (lack of impurities) and the intensely white color of the aggregates also increase the specimen's value. ## Popular Localities The Solongo deposit in Russia is the sole source of collector specimens. Material from this locality is the standard for this mineral species.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using only a soft brush to remove dust. Due to possible reactivity with water, wet cleaning should be avoided. If absolutely necessary, a minimal amount of isopropyl alcohol on a cotton swab can be used, ensuring rapid evaporation. ## What to Avoid Contact with water and acids, which can damage or dissolve the mineral, must be strictly avoided. Fedorovskite is relatively soft and brittle, so it must be protected from impacts, scratching, and vibrations. It should not be heated or exposed to prolonged moisture. ## Storage It is recommended to store specimens in a dry place, preferably in a closed display box away from dust and moisture. Due to its brittleness, it should not be stored in contact with harder minerals.

Sources

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