Thionasilite

Chemical formula: Na<sub>2</sub>Si<sub>2</sub>S<sup>2-</sup><sub>2</sub>O<sub>3</sub>

Thionasylite is an extremely rare sodium sulfosilicatemineral, known exclusively from one locality in the world – the Khibiny Massif in Russia.

## Characteristics Thionasylite is a mineral with a unique chemical composition, combining silicates and sulfides. It forms very fine, granular aggregates or poorly developed, lath-like crystals, reaching up to 0.3 mm in size. It typically occurs as inclusions in other minerals, mainly ussingite. It is a brittle mineral. ## Physical Properties Due to its extreme rarity and small crystal size, many of thionasylite's physical properties have not been fully investigated. It has a vitreous luster and is transparent to translucent. Its hardness and density have not been precisely determined. ## Colors and Varieties This mineral is colorless or pale yellow. No varieties are known. ## History and Name The name thionasylite refers to its chemical composition: it contains sulfur (Greek *thion*), sodium (*natrium*), and silicon (*silicium*). It was approved as a new mineral species by the International Mineralogical Association (IMA) in 2007. It was described by a team of mineralogists: N.V. Chukanov, I.V. Pekov, A.E. Zadov, V.V. Zubkova, S.N. Britvin, D.Y. Pushcharovsky. ## Applications Thionasylite has no industrial applications. Due to its extreme rarity and microscopic size, it is of interest only to specialized collectors and scientific institutions.

Properties

Luster
Vitreous
Streak
White
Cleavage
Perfect on {100}
Transparency
Transparent to Translucent
Crystal system
Triclinic

Diagnostic features

## Identification Identification of thionasylite is impossible without advanced analytical methods, such as Raman spectroscopy or chemical analysis using an electron microprobe (EDS/WDS). Visually, it is a colorless or pale yellow mineral forming fine inclusions in ussingite. Its key feature is its unique chemical composition. ## Distinguishing from Similar Minerals Due to its occurrence as fine inclusions, it can be confused with many other microminerals. Definitive differentiation from other colorless or yellowish minerals co-occurring in Khibiny pegmatites (e.g., natrosilite, makatite) requires specialized research equipment. ## Crystal Forms Thionasylite forms poorly developed, lath-like or tabular crystals not exceeding 0.3 mm in size. Most often, it occurs as irregular grains and aggregates embedded in other minerals.

Geological environment

## Genesis Thionasylite forms in strongly alkaline, differentiated agpaitic pegmatites. It is a product of hydrothermal processes occurring in the late stage of crystallization of these pegmatites, under conditions of extremely high sodium activity and low silica activity. ## Mineral Associations This mineral occurs in close association with ussingite (in which it forms inclusions), lomonosovite, eudialyte, sodalite, aegirine, natrosilite, makatite, rasvumite, villiaumite, and sphalerite. ## Localities The only confirmed locality of thionasylite in the world is its type locality: the Khibiny Massif on the Kola Peninsula in Russia. It was found there in pegmatites within Mount Koashva.

Rarity

Extremely rare

For collectors

## Quality Criteria In the case of such a rare micromineral as thionasylite, the only criterion for evaluation is its presence and identifiability. The most highly valued specimens are those where thionasylite is as "rich" as possible (visible in larger quantities or as larger grains) and well-documented analytically. Association with other rare minerals from this locality also increases the scientific and collector's value of the specimen. ## Popular Localities All collector material originates from a single location in the world – Mount Koashva in the Khibiny Massif on the Kola Peninsula in Russia.

Care and storage

## Cleaning Specimens containing thionasylite, due to their microscopic nature and fragility, should generally not be mechanically cleaned. If absolutely necessary, compressed air (from a safe distance) can be used to remove dust. Contact with water and chemicals should be avoided. ## What to Avoid This mineral is potentially unstable in humid air and may decompose. Contact with water, acids, bases, and other chemicals must be strictly avoided. It should not be heated or exposed to prolonged sunlight. ## Storage Thionasylite specimens must be stored in dry conditions, preferably in sealed containers (e.g., "perky boxes") with a desiccant such as silica gel. Store at a stable temperature, away from light.

Sources

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