Alexkhomyakovite

Chemical formula: K<sub>6</sub>(Ca<sub>2</sub>Na)(CO<sub>3</sub>)<sub>5</sub>Cl·6H<sub>2</sub>O

A very rare hydrated potassium, calcium, and sodium carbonate, forming brittle, colorless, platy crystals in alkaline pegmatites.

## Characteristics Alexkhomyakovite is a complex, hydrated carbonate with a complicated chemical composition. It occurs as very small, thin, platy crystals with a hexagonal outline. Crystals are typically colorless or white and transparent. Due to their small size, specimens appear as tiny flakes gathered in groups, rosettes, or spherical aggregates on the surface of other minerals. ## Physical Properties This mineral is extremely soft and brittle. It exhibits a vitreous luster on crystal faces and a pearly luster on planes of perfect cleavage. Its density is approximately 2.41 g/cm³. It is unstable under atmospheric conditions – it readily dehydrates (loses water) in dry air and is soluble in water. ## Colors and Varieties Alexkhomyakovite is usually colorless, less commonly white. No color varieties or commercial varieties are distinguished. ## History and Name The mineral was approved by the International Mineralogical Association (IMA) in 2006. Its name honors Alexander Petrovich Khomyakov (1933–2012), a prominent Russian mineralogist and researcher of minerals from the alkaline massifs of the Kola Peninsula, who discovered and described dozens of new minerals. ## Uses Alexkhomyakovite has no industrial application. It is solely an object of scientific research and is valued in specialized collections of rare minerals.

Properties

Luster
Vitreous, Pearly
Streak
White
Density
2.41
Cleavage
Perfect on {0001}
Transparency
Transparent
Crystal system
Trigonal

Diagnostic features

## Identification Characteristic features include crystal form (thin, hexagonal plates), perfect cleavage in one direction, vitreous-pearly luster, and a specific environment of occurrence. A key, though destructive, diagnostic feature is its solubility in water. It reacts violently with the release of bubbles (effervesces) upon contact with dilute hydrochloric acid. ## Distinguishing from Similar Minerals It can be confused with other colorless, platy minerals from alkaline environments, such as natrite or thermonatrite. Certain differentiation from these is usually impossible without advanced studies, such as chemical composition analysis (EDS) or X-ray diffraction (XRD). ## Crystal Forms It forms thin, platy or lamellar crystals with a hexagonal outline. Crystals often arrange into stacks, fan-like groups, rosettes, or spherical aggregates.

Geological environment

## Genesis Alexkhomyakovite is a hydrothermal mineral, crystallizing in the late stage of pegmatite evolution within ultra-alkaline massifs (so-called hyperagpaitic pegmatites). It forms in rock cavities and fissures. ## Mineral Associations It most commonly co-occurs with other rare alkaline minerals, such as natrite, thermonatrite, shortite, ewaldite, villiaumite, rasvumite, and sidorenkite. ## Localities This is an extremely rare mineral, known practically only from two localities in the world, both located on the Kola Peninsula in Russia. These are the alkaline massifs: Khibiny (mainly the Koashva deposit and Mount Rasvumchorr) and Lovozero (Mount Alluaiv).

Rarity

Very rare

For collectors

## Quality Criteria As a micromount mineral, its collector's value depends on several factors. Specimens with well-formed, sharp, and undamaged crystals are most highly prized. The size and richness of the aggregate are also important – the more crystals on the rock matrix, the better. Transparency and aesthetic arrangement (e.g., in the form of a rosette) significantly increase the attractiveness of the specimen. Co-occurrence with other rare minerals adds significant value. ## Popular Localities The only source of collector specimens is the localities on the Kola Peninsula in Russia, primarily the Koashva mine in the Khibiny Massif.

Care and storage

## Cleaning The mineral is soluble in water, therefore **it must absolutely not be cleaned wet**. Any contact with water or even humid air can damage or destroy it. Mechanical cleaning is highly risky due to its extreme brittleness; if necessary, a soft brush or compressed air from a distance can be carefully used. ## What to Avoid Avoid contact with water, water vapor, and all liquids. The mineral is sensitive to changes in humidity – in dry air, it dehydrates and can crumble into powder. It must be protected from acids, with which it reacts violently. It is very brittle, so avoid shocks and touching. ## Storage Alexkhomyakovite specimens must be stored in tightly sealed containers to isolate them from atmospheric humidity fluctuations. Specialized "micromount" boxes or other airtight packaging are the best solution. It should be stored at a stable temperature, away from direct sunlight.

Sources

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