Shomiokite-(Y)

Chemical formula: Na₃Y(CO₃)₃·₃H₂O

Shomiokite-(Y) is a rare, hydrated sodium and yttrium carbonate, forming characteristic, radial aggregates of colorless or white crystals.

## Characteristics Shomiokite-(Y) is a rare mineral from the carbonate group, chemically classified as a hydrated sodium and yttrium carbonate. Its most typical and recognizable form consists of radial or stellate aggregates, resembling rosettes, composed of tabular or short-prismatic crystals. Specimens are usually colorless, white, or grayish, exhibiting high transparency. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of 2-3, making it susceptible to scratching. It has a vitreous luster on crystal faces and a density of approximately 2.65 g/cm³. It is transparent to translucent. ## Colors and Varieties Shomiokite-(Y) occurs in a limited color palette – it is colorless, white, or takes on shades of gray. There are no named color varieties or commercial varieties. ## History and Name The mineral was first described in 1996 by A.P. Khomyakov and co-workers. Its name comes from the Shomiok River, flowing near the discovery site on Mount Koashva in the Khibiny Massif on the Kola Peninsula, Russia. The -(Y) suffix in the name indicates that yttrium is the dominant rare-earth element in its structure. ## Applications Due to its rarity, small crystal size, and fragility, shomiokite-(Y) has no industrial applications. It is solely an object of scientific interest and a valued acquisition for advanced systematic and regional mineral collections.

Properties

Mohs hardness: 2-3
Luster: Vitreous
Streak: White
Density: 2.65
Cleavage: Perfect on {010}
Fracture: Uneven
Transparency: Transparent to Translucent
Crystal system: Orthorhombic

Diagnostic features

## Identification Characteristic features of shomiokite-(Y) include its unique, radial crystal aggregates, low hardness, and occurrence in a specific geological environment of agpaitic pegmatites. It reacts violently with hydrochloric acid, releasing carbon dioxide. Perfect cleavage in one direction is also a helpful indicator. ## Distinguishing from Similar Minerals Shomiokite-(Y) can be confused with other rare carbonates found in the same environment, such as mckelveyite-(Y) or sidorenkite. McKelveyite-(Y) crystallizes in the trigonal system and often forms more complex, barrel-shaped crystals. Sidorenkite crystallizes in the monoclinic system. Certain differentiation of these minerals in many cases requires advanced analytical methods, such as X-ray diffraction (XRD). ## Crystal Forms Crystals are tabular or short-prismatic, almost always gathered in radial, stellate, or spherulitic aggregates and rosettes. Single, well-formed crystals are extremely rare.

Geological environment

## Genesis Shomiokite-(Y) is a hydrothermal mineral, crystallizing at low temperatures. It forms in voids and caverns within ultra-agpaitic pegmatites that cut nepheline syenites. It is one of the last minerals to form during the pegmatite crystallization process. ## Mineral Associations This mineral co-occurs with other rare alkaline minerals typical of pegmatites from the Khibiny and Lovozero massifs. The most common associations include sidorenkite, mckelveyite-(Y), natron, thermonatrite, kogarkoite, ewaldite, and villiaumite. ## Localities The most important and practically only significant occurrences of shomiokite-(Y) in the world are located on the Kola Peninsula in Russia. These are the alkaline massifs of Khibiny (Koashva mine, Yukspor Mountain) and Lovozero (Alluaiv Mountain), from where the best collector specimens originate.

Rarity

Very rare

For collectors

## Quality Criteria The most highly valued shomiokite-(Y) specimens are those that form well-defined, sharp, and complete rosettes at least several millimeters in diameter. The transparency and luster of the crystals forming the aggregate are important. Specimens on matrix, contrasting with the substrate, and associations with other rare minerals (e.g., red villiaumite) are particularly sought after by collectors. ## Popular Localities The best specimens in the world are considered to come from ultra-agpaitic pegmatites in the Koashva mine in the Khibiny Massif and from Alluaiv Mountain in the Lovozero Massif on the Kola Peninsula, Russia. These are classic localities for this mineral.

Care and storage

## Cleaning Shomiokite-(Y) is partially soluble in water, therefore, cleaning must be done exclusively dry. To remove dust, use a soft brush or compressed air from a safe distance. Any contact with water or cleaning fluids is unacceptable. ## What to Avoid Contact with water, acids (it reacts violently), and any chemicals must be absolutely avoided. The mineral is very sensitive to humidity changes, which can lead to its dehydration and disintegration. It is also very soft and brittle, and its perfect cleavage makes it susceptible to mechanical damage. ## Storage Shomiokite-(Y) specimens are best stored in tightly sealed containers (e.g., perky boxes) to protect them from dust and fluctuations in air humidity. It is recommended to keep them in stable conditions, away from heat sources and direct sunlight.

Sources

IMA Mineral List (CNMNC)