Popugaevaite

Chemical formula: Ca₃[B₅O₆(OH)₆]FCl₂·8H₂O

Popugaevite is a very rare, hydrated calcium borate, forming colorless, tabular crystals with a vitreous luster.

## Characteristics Popugaevite is an extremely rare mineral from the borate group. It occurs as small, colorless, tabular crystals, reaching sizes up to 0.3 x 0.2 x 0.05 mm. The crystals are transparent and characterized by a vitreous luster. They typically form irregular aggregates or grow on other minerals. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of 3. It is brittle, and its density is slightly greater than that of quartz. The crystals exhibit perfect cleavage in one direction. ## History and Name The mineral is named in honor of Klara Nikolaevna Popugaeva (1920-1996), a Russian geologist who, in 1954, discovered the first diamond deposit in Yakutia (the Zarnitsa kimberlite pipe) using the indicator mineral prospecting method. Popugaevite was approved as a new mineral species by the IMA in 2018 (IMA2018-043).

Properties

Mohs hardness
3-0
Color
colorless
Luster
Vitreous
Streak
white
Density
1.933
Cleavage
{010}
Fracture
Step-Like
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of popugaevite is possible almost exclusively through advanced analytical methods, such as X-ray diffraction (XRD) and chemical spectroscopy (EDS/WDS), due to its microscopic size and occurrence in complex parageneses. Visually, it is a colorless, tabular mineral with a vitreous luster. ## Distinguishing from similar minerals It can be confused with other colorless, secondary borate or sulfate minerals found in the same environment, such as ginorite or gypsum. Differentiation without specialized equipment is practically impossible. Association with its unique locality and accompanying minerals is key. ## Crystal forms It forms thin, tabular crystals with a hexagonal outline, often in irregular aggregates.

Geological environment

## Genesis Popugaevite forms as a secondary mineral in the weathering zones of boron deposits. In its only known locality (Solongo mine), it forms as a result of supergene processes (surface weathering) acting on primary borate mineralization within magnesian skarns. ## Mineral associations This mineral co-occurs with other borates, such as ginorite, frolovite, pentahydroborite, wimlanarkite, as well as calcite and magnetite. ## Localities The only confirmed occurrence of popugaevite in the world is the Solongo boron deposit, located in the Republic of Buryatia, Russia.

Rarity

Extremely rare

For collectors

## Quality criteria Due to its extreme rarity and microscopic size, every analytically confirmed popugaevite specimen is extremely valuable from a scientific and collector's perspective. Specimens with the largest, well-formed crystals, clearly visible on the rock matrix, and correctly identified would be most highly prized. The richness of aggregates and association with other rare borates also increase the specimen's value.

Care and storage

## Cleaning Due to its extreme rarity and delicacy, popugaevite specimens should only be cleaned by specialists. If absolutely necessary, compressed air (from a safe distance) can be used to remove loose dust particles. Any contact with water or other liquids should be avoided. ## What to avoid The mineral is brittle and soft, so it must be protected from impacts and scratches. As a hydrated borate, it can be sensitive to changes in humidity and elevated temperatures, which can lead to dehydration and damage. Contact with chemicals and ultrasonic cleaning should be strictly avoided. ## Storage Specimens should be stored in stable conditions, in enclosed, padded "micromount" boxes, protecting them from dust, vibrations, and sudden changes in temperature and humidity. Display should only take place in specialized display cases with controlled environments.

External references

Sources

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