Oulankaite
Chemical formula: Pd<sub>5</sub>Cu<sub>4</sub>SnTe<sub>2</sub>S<sub>2</sub>
Oulankaite is an extremely rare palladium, copper, tin, tellurium, and sulfur mineral, occurring as microscopic grains in igneous rocks.
Description
## Characteristics Oulankaite is a very rare mineral from the sulfosalt group, with a complex chemical composition containing palladium, copper, tin, tellurium, and sulfur. It occurs as microscopic, irregular (anhedral) grains, usually not exceeding 100-200 micrometers in size. It is opaque and has a metallic luster. Its color in reflected light is described as creamy white with a slight tint, sometimes grayish white. Due to its size, it is a mineral that can only be observed and identified using advanced microscopic techniques. ## Physical Properties This mineral is characterized by a hardness of approximately 5 on the Mohs scale. Its density is high, around 9.35 g/cm³, which is typical for minerals containing platinum group metals. It possesses a strong, metallic luster. It is a brittle mineral. ## Colors and Varieties Oulankaite has a consistent, creamy white or grayish white color. It does not form colored varieties or commercial grades. ## History and Name The mineral's name comes from its discovery locality – the Oulanka igneous complex, specifically from the Lukkulaisvaara intrusion, on the border of Finland and Russia (Republic of Karelia). It was first described in 1999 by a team of mineralogists led by A.Y. Barkov. Its status and chemical formula were subject to further research and were updated in later years. ## Applications Due to its extreme rarity and occurrence only as microscopic grains, oulankaite has no industrial application. It is solely an object of scientific interest, helping to understand the geochemical processes leading to the concentration of platinum group elements, and is a valuable acquisition for specialized collectors of microscopic minerals (so-called micromounts).
Diagnostic features
## Identification Identification of oulankaite is impossible without specialized equipment. Recognition is based on chemical analysis using an electron microprobe (EDS/WDS), which allows its unique composition to be determined. In studies under a reflected light microscope, it is characterized by a creamy white color, metallic luster, and high reflectivity. A key indicator is its occurrence in a specific paragenesis of platinum group minerals. ## Distinguishing from Similar Minerals Oulankaite can be easily confused with other rare platinum group minerals with a similar appearance in reflected light, such as kotulskite, sobolevskite, merenskyite, or other tellurides and palladium alloys. Certain distinction is only possible based on precise chemical composition analysis. ## Crystal Forms This mineral does not form well-developed crystals. It occurs exclusively as anhedral (irregular, xenomorphic) grains, often as inclusions in other minerals, mainly in copper and iron sulfides, or forming intergrowths with other platinum group minerals.
Geological environment
## Genesis Oulankaite is a mineral of magmatic origin. It forms in the final stages of crystallization within differentiated mafic and ultramafic intrusions that are enriched in platinum group elements (PGE). Its crystallization is associated with the segregation of sulfides and tellurides from residual, volatile- and PGE-rich magma. ## Mineral Associations This mineral occurs in association with other platinum group minerals and base metal sulfides. Its most common associations include: chalcopyrite, bornite, pentlandite, kotulskite, sobolevskite, merenskyite, tellurohauchecornite, as well as gold and silver alloys (electrum). ## Localities Oulankaite is an extremely rare mineral, confirmed in only a few locations worldwide. The main, verified occurrences are: - **Russia**: Lukkulaisvaara intrusion within the Oulanka complex in Karelia (type locality). - **Finland**: Kirakkajuppura PGE deposit in the Penikat intrusion, near Kemi.
Rarity
Extremely rare
Collector aspects
## Quality Criteria For such a rare micromineral as oulankaite, the primary criterion for value is certainty of identification, confirmed by chemical analysis. Collectible specimens are most often fragments of parent rock or polished thin sections. The attractiveness of a specimen is determined by the size and richness of oulankaite grain aggregates, as well as the presence of well-defined associated minerals, especially other rare platinum group minerals. The purity of the grain itself is not crucial; the mineralogical context is more important. ## Popular Localities The vast majority of material available in scientific and specialized collections comes from two main localities: the Lukkulaisvaara intrusion in Russia and the Kirakkajuppura deposit in Finland. Specimens from these locations are most valued due to their scientific significance and status as type or reference localities.
Care and storage
## Cleaning Oulankaite specimens are typically polished petrographic thin sections or rock fragments with microscopic grains. They do not require cleaning. For dusty parent rock specimens, dust can be gently removed with a soft brush or a photographic air blower. Avoid contact with water and any chemical agents. ## What to Avoid Contact with acids and other aggressive chemicals, which can destroy not only the mineral itself but also its associated sulfides and tellurides, must be strictly avoided. As a sulfur-containing mineral, it may be susceptible to oxidation in a humid environment, so humidity should be avoided. It should not be subjected to ultrasonic cleaning. ## Storage Specimens containing oulankaite are best stored in a dry and stable environment. An ideal solution is a sealed "micromount" box, which protects against dust, humidity, and accidental mechanical damage.