Kashinite

Chemical formula: Ir₃+₂S₂-₃

Kashinite is a very rare iridium sulfide, occurring as fine, metallic grains within ultramafic rocks.

## Characteristics Kashinite is an extremely rare sulfide mineral, chemically defined as iridium sulfide. It occurs as very small, anhedral (not exhibiting its own crystallographic form) grains, usually not exceeding 0.2 mm in size. Its grains are most often intergrown with other minerals, mainly chromite. Due to its composition and rarity, it is of purely scientific and collector's interest. ## Physical Properties This mineral is characterized by a metallic luster and black color. It is opaque. Its Mohs hardness is high, at 7. The density is also very high, which is typical for minerals containing platinum group metals, and is 8.82 g/cm³. ## History and Name Kashinite was first described in 1976 by A.D. Genkin and his colleagues. The mineral's name honors Stepan Alexandrovich Kashin (1900-1972), a Russian mineralogist and specialist in platinum group metal deposits, who worked at the Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry (IGEM) in Moscow. It was approved by the International Mineralogical Association (IMA) in the same year.

Properties

Mohs hardness: 7
Luster: Metallic
Streak: Black
Density: 8.82
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Orthorhombic

Diagnostic features

## Identification Identification of kashinite is impossible without advanced laboratory techniques. It requires analysis by electron microprobe (EDS/WDS) to confirm its chemical composition (the presence of iridium and sulfur in appropriate proportions). In polished sections under a reflected light microscope, it exhibits a creamy white color and is anisotropic. ## Distinguishing from Similar Minerals It can be confused with other opaque, metallic platinum group minerals, such as cuproiridsite, malanite, or laurite, with which it often co-occurs. Definitive differentiation is only possible based on detailed chemical and crystallographic analysis. ## Crystal Forms Kashinite occurs exclusively as anhedral, irregular grains, often forming aggregates with other platinum group metal sulfides.

Geological environment

## Genesis Kashinite is a mineral of magmatic origin. It forms in dunite-harzburgite ophiolite complexes and layered intrusions, where it crystallizes along with other platinum group minerals from ultramafic magma. ## Mineral Associations It most commonly co-occurs with chromite, in which it forms inclusions. It is also accompanied by other platinum group minerals, such as laurite, irarsite, cuproiridsite, malanite, as well as osmium, iridium, and ruthenium alloys. ## Localities The most important occurrences of this mineral include its type locality in the Gusevogorskoye massif in the Urals, Russia. It has also been reported in the Bushveld Complex in South Africa, the Stillwater Complex in Montana (USA), Thetford Mines in Quebec (Canada), and in chromite deposits in Albania and the Philippines.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a kashinite specimen is determined not by the appearance of the mineral itself (which is microscopic), but by the richness of the mineral association and the confirmation of its presence through analysis. The most valuable samples are those from the type locality or those that contain well-documented, rich concentrations of various platinum group minerals. The specimen has purely scientific and systematic value. ## Popular Localities The only sources of specimens reaching the collector's market are historical localities, mainly from Russia (Urals) and South Africa (Bushveld Complex).

Care and storage

## Cleaning Due to the extreme rarity and small size of the grains, which are typically intergrown within the rock matrix, mechanical cleaning of individual kashinite grains is practically impossible and inadvisable. Specimens in the host rock can only be cleaned very carefully, using compressed air to remove dust. ## What to Avoid Contact with chemicals, especially strong acids, which could damage both kashinite and its associated minerals, should be avoided. Specimens should not be subjected to ultrasonic cleaning or high temperatures. ## Storage Specimens containing kashinite should be stored under stable conditions, in sealed containers or display cases, to protect them from dust and contaminants. Due to their scientific value and rarity, minimizing handling is recommended.

Sources

IMA Mineral List (CNMNC)