Kojonenite

Chemical formula: Pd<sub>₇-x</sub>SnTe<sub>₂</sub> (₀.₃ ≤ x ≤ ₀.₈)

Kojonenite is a rare palladium tin telluride, forming small, hexagonal crystals with a metallic luster, found in platinum group metal deposits.

## Characteristics Kojonenite is a very rare mineral from the telluride group, chemically classified as a palladium tin telluride. It occurs as very small, hexagonal grains or plates, rarely exceeding 0.1 mm. It is most often observed as inclusions in other minerals, especially in sobolevskite. Its appearance is typically metallic, with a color ranging from white to gray with a creamy tint. ## Physical Properties This mineral is characterized by a strong, metallic luster. It is opaque. Due to the extremely small size of its crystals, most of its physical properties, such as hardness or density, have not been precisely measured, but only calculated based on its chemical composition and crystal structure. The calculated density is approximately 10.36 g/cm³. ## Colors and Varieties In reflected light, kojonenite is white to creamy white, often with a gray tint. It does not exhibit pleochroism. No colored or commercial varieties are known. ## History and Name Kojonenite was first described in 1997 by G. A. Desborough, J. L. Czamanske, and K. J. T. Livi. The mineral is named in honor of Finnish mineralogist Kari K. Kojonen (born 1944), a specialist in the mineralogy of ore and platinum group metals, in recognition of his contributions to deposit research in Finland. ## Uses Kojonenite has no industrial application due to its extreme rarity and microscopic size. It is of purely scientific interest and is an object of interest for specialized collectors of micromount minerals.

Properties

Luster: Metallic
Streak: Black
Density: 10.36
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Hexagonal

Diagnostic features

## Identification Identification of kojonenite is only possible using advanced laboratory techniques, such as reflected light ore microscopy and chemical analysis using an electron microprobe (EDS/WDS). Its characteristic feature is the co-occurrence of palladium, tin, and tellurium in specific proportions. ## Distinguishing from Similar Minerals Under the microscope, it can be confused with other platinum group metal tellurides, such as kotulskite (Pd(Te,Bi)), merenskyite (PdTe₂), or sobolevskite (PdBi). Definitive differentiation requires chemical composition analysis, as their optical properties are very similar. ## Crystal Forms Kojonenite forms very small, hexagonal crystals with a tabular or platy habit. It usually occurs as irregular grains or as inclusions in other minerals, forming intergrowths with them.

Geological environment

## Genesis Kojonenite crystallizes in the late stages of magmatic processes within mafic and ultramafic intrusions, rich in platinum group elements (PGE). It forms under low-temperature conditions (below 400°C) as a result of reactions between residual, hydrothermal fluids and previously crystallized sulfides and arsenides. ## Mineral Associations This mineral most often occurs in association with other platinum group minerals. Typical associated minerals include sobolevskite, kotulskite, chalcopyrite, pentlandite, as well as native gold, native platinum, and other rare tellurides and bismuthides. ## Localities As an extremely rare mineral, kojonenite has been identified in only a few locations worldwide. The type locality is the Stillwater Complex in Montana, USA. Other confirmed occurrences include the Lukkulaisvaara deposit in Karelia (Russia) and the Koillismaa intrusion in Finland.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a kojonenite specimen is assessed primarily based on its identification and documentation. Since it occurs in microscopic form, the certainty of mineral identification, confirmed by chemical analysis, is paramount. The richness of its association with other rare platinum group minerals on a single piece of host rock enhances its attractiveness. ## Popular Localities The most "classic" specimens, including the type material, come from the Stillwater Complex in Montana, USA. However, these are practically unavailable on the collector's market and are mainly found in institutional collections.

Care and storage

## Cleaning Kojonenite specimens occur as microscopic inclusions in other minerals and do not require cleaning. Any attempt at mechanical or chemical cleaning would destroy the delicate specimen. ## What to Avoid Avoid contact with chemicals, acids, and ultrasound. Temperature and humidity changes do not have a major impact, but the host rock specimen should be protected from mechanical damage. ## Storage Micromount specimens of kojonenite should be stored in specialized "micromount" boxes, protecting them from dust and physical damage. Avoid vibrations and shocks.

Sources

IMA Mineral List (CNMNC)