Irinarassite

Chemical formula: Ca₃Sn₄+₂(Al₂Si)O₁₂

Irinarassite is a rare garnet group mineral, distinguished by the presence of tin in its chemical composition and its occurrence as microscopic, yellowish grains.

## Characteristics Irinarassite is a mineral belonging to the garnet supergroup. It forms very small, individual, isometric grains, usually not exceeding 0.1 mm in size. It most often occurs as inclusions in other minerals. Due to the microscopic size of the crystals, its visual features are difficult to observe without specialized equipment. ## Physical Properties The crystals exhibit a vitreous luster. The mineral's hardness is high, estimated at about 7 on the Mohs scale, which is typical for garnets. The density is significantly higher than average for this group, at approximately 4.12 g/cm³, which is due to the presence of the heavy element — tin. ## Colors and Varieties Observed irinarassite grains range in color from pale yellow to yellowish-green. No varieties of this mineral have been distinguished. ## History and Name The mineral's name honors Irina Teodorovna Rass, a Russian geologist and petrologist specializing in the study of alkaline rocks and carbonatites. Irinarassite was officially recognized by the International Mineralogical Association (IMA) in 2009. It was discovered in material from the Inagli massif on the Aldan Shield in Yakutia (Russia). ## Applications Irinarassite has no industrial or commercial applications. Its significance is purely scientific and as a collector's item, as a rare member of the garnet group.

Properties

Mohs hardness: 7
Luster: Vitreous
Streak: White
Density: 4.12
Cleavage: None
Fracture: Uneven
Transparency: Transparent to translucent
Crystal system: Cubic

Diagnostic features

## Identification Identification of irinarassite is impossible without advanced analytical techniques. It requires chemical analysis (e.g., using an electron microprobe) to confirm its unique composition with a dominance of calcium and tin. Optically, under a microscope, small, isotropic grains with a high refractive index can be observed. ## Distinguishing from Similar Minerals It can be confused with other tin-bearing garnets, such as bitikleite or dzhuluite, from which it differs by subtle variations in chemical composition, especially in aluminum and silicon content. Visually, it is indistinguishable from other fine-grained, yellowish garnets. ## Crystal Forms Irinarassite forms single, equant (isometric) crystals, often with a rhombic dodecahedral habit, typical for garnets. They occur as disseminated, microscopic grains.

Geological environment

## Genesis Irinarassite forms under specific metasomatic conditions, within rocks called fenites. These are rocks formed by the interaction of fluids derived from alkaline or carbonatitic intrusions with surrounding silica-rich rocks. The presence of tin is crucial for its crystallization. ## Mineral Associations This mineral coexists with mica (phlogopite), pyroxenes (diopside), scapolite, titanite, apatite, calcite, and other rare tin minerals such as malayaite and cassiterite. ## Localities The only confirmed occurrence of irinarassite in the world is its type locality – the Inagli alkaline-ultrabasic massif, located on the Aldan Shield in southern Yakutia, Russia.

Rarity

Very rare

For collectors

## Quality Criteria As a microscopic mineral, irinarassite is not evaluated by typical criteria such as size or color. Specimens in which the presence of the mineral has been analytically confirmed hold the greatest value. The richness of irinarassite grains visible under a microscope and its association with other rare minerals enhance its appeal. ## Popular Localities The only source of specimens is the Inagli massif in Russia. Material from this locality is extremely rarely available on the collector's market and is sought primarily by specialized scientific institutions and collectors of "systematic" and microminerals.

Care and storage

## Cleaning Due to its microscopic size and occurrence as inclusions in the host rock, individual crystals are not subject to cleaning. The host rock specimen can be cleaned with a soft brush and distilled water. ## What to Avoid Avoid contact with strong acids, which could damage the host rock. Despite its high hardness, the specimen should be protected from impacts and abrasion, which could damage the delicate, microscopic crystals. ## Storage Specimens containing irinarassite should be stored in stable conditions, away from dust and moisture, preferably in a closed display box. A label with precise locality information is crucial for the scientific value of the specimen.

Sources

IMA Mineral List (CNMNC)