Arzamastsevite

Chemical formula: K₆Al₅Si₆O₂₀(OH)₄Cl

Arzamastsevite is a very rare silicate mineral, found as small, colorless to white crystals in alkaline massifs.

## Characteristics Arzamastsevite is a complex potassium and aluminum silicate, belonging to the group of very rare minerals. It occurs as very small, tabular or lath-like crystals, usually not exceeding 0.3 mm in length. The crystals are colorless to white and form aggregates or occur as inclusions in other minerals, such as aegirine. Due to its size and rarity, it is a mineral of purely scientific and collectible interest. ## Physical Properties Arzamastsevite crystals exhibit a vitreous luster. They are transparent to translucent. The Mohs hardness is approximately 3, and the density is close to 2.61 g/cm³. This mineral does not show fluorescence under ultraviolet light. ## History and Name Arzamastsevite was discovered and described in 2017. Its name honors Mikhail Vladimirovich Arzamastsev, a Russian geologist and specialist in the petrology of alkaline rocks, for his contribution to the study of the Khibiny Massif on the Kola Peninsula, where this mineral was first found. ## Applications Arzamastsevite has no industrial applications. It is an object of interest for specialized collectors of rare minerals (so-called micromounts) and scientists studying the petrology and mineralogy of alkaline massifs.

Properties

Mohs hardness: 3
Luster: Vitreous
Streak: White
Density: 2.61
Cleavage: Good on {100}
Fracture: Uneven
Transparency: Transparent to translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of arzamastsevite is possible only by advanced analytical methods, such as X-ray diffraction (XRD) and electron microprobe analysis (EMPA). Visual identification in the field or even in a collection is impossible due to the microscopic size of the crystals and their similarity to many other white silicates. ## Distinguishing from similar minerals It can be confused with many other microscopic minerals found in similar environments, such as cancrinite, natrolite, or other zeolites. Certain differentiation requires specialized laboratory equipment. ## Crystal forms Arzamastsevite forms very small, thin, tabular or lath-like crystals, often grouped into small, radial or chaotic aggregates. Crystals rarely exceed 0.3 mm in length and 0.02 mm in thickness.

Geological environment

## Genesis Arzamastsevite forms in the late stages of hydrothermal processes in highly differentiated alkaline massifs. It is found in pegmatites and hydrothermal veins cutting nepheline syenites. ## Mineral associations This mineral coexists with aegirine, sodalite, microcline, nepheline, eudialyte, lorenzenite, lamprophyllite, as well as rarer minerals such as kazakovite, rasvumite, and villiaumite. ## Localities The only confirmed occurrence of arzamastsevite in the world is its type locality - Mount Nyorkpakhk (Niorkpakhk) in the Khibiny Massif on the Kola Peninsula in Russia.

Rarity

Very rare

For collectors

## Quality criteria As a "micromount" type mineral, the collectible value of arzamastsevite primarily depends on the quality of the host specimen and the richness of the mineral association. The most desirable specimens are those on which well-formed, albeit microscopic, aggregates of arzamastsevite crystals are visible, clearly contrasting with the matrix (e.g., dark aegirine). The certainty of identification, confirmed by the discoverer or a laboratory, is also crucial. ## Popular localities The only source of specimens is the Khibiny Massif on the Kola Peninsula in Russia. Specimens from this locality are the only authentic ones on the collector's market.

Care and storage

## Cleaning Specimens with arzamastsevite, usually micromounts, do not require cleaning. If absolutely necessary, compressed air can be used to remove dust. Avoid contact with water and any chemicals. ## What to avoid As a mineral with low hardness, it is very susceptible to mechanical damage. Avoid contact with hard objects, ultrasound, and any cleaning fluids. Protect it from high temperatures and humidity. ## Storage Arzamastsevite specimens should be stored exclusively in specialized micromount boxes that protect them from dust, shocks, and mechanical damage. Display is not recommended due to the small size of the crystals.

Sources

IMA Mineral List (CNMNC)