Atokite

Chemical formula: Pd<sub>3</sub>Sn

Atokite is a rare mineral from the native elements group, a natural alloy of palladium and tin, occurring as small, metallic grains.

## Characteristics Atokite is a rare mineral from the native elements group, classified as a natural alloy (intermetallic compound) of palladium and tin. It typically occurs as small, irregular grains or as coatings on other minerals, mainly platinum-group metal sulfides. Its crystals, observed only on a microscopic scale, have cubic or octahedral forms. It is an opaque mineral with a metallic luster. ## Physical Properties Atokite is characterized by a Mohs hardness of 5. It is a heavy mineral, with a calculated density of 14.97 g/cm³, which is typical for platinum-group metal alloys. It does not exhibit cleavage, and its fracture is hackly. It is ductile and malleable. ## Colors and Varieties This mineral has a color ranging from white to silvery-white, often with a yellowish or creamy tint. In reflected light, its color is white with a creamy tone. No color varieties or commercial varieties are distinguished. ## History and Name Atokite was first described in 1975 by P. Mihálik, S. A. Hiemstra, and J. P. R. de Villiers. Its name comes from its discovery locality – the Atok platinum mine (now Bokoni) in the Bushveld Igneous Complex in the Republic of South Africa. It was approved as a new mineral by the International Mineralogical Association (IMA) in the same year. ## Applications Due to its extreme rarity, atokite has no industrial applications. However, it is an object of scientific interest and is valued by specialized collectors of platinum-group minerals.

Properties

Mohs hardness
5
Luster
Metallic
Streak
Black
Density
14.97
Cleavage
None
Fracture
Hackly
Transparency
Opaque
Crystal system
Cubic

Diagnostic features

## Identification Identification of atokite is possible almost exclusively through advanced laboratory methods, such as reflected light analysis (ore microscopy) and chemical analysis using an electron microprobe (EDS/WDS). Under the microscope, it is distinguished by its creamy-white color and high reflectivity. It is isotropic. ## Distinguishing from Similar Minerals Atokite is visually indistinguishable from other bright platinum-group minerals, such as rustenburgite (Pt₃Sn), with which it forms a solid solution, or native platinum. Definitive differentiation requires chemical composition analysis, which allows for determining the dominance of palladium and tin in an atomic ratio close to 3:1. ## Crystal Forms Atokite crystallizes in the isometric system. It is observed as very small, irregular grains, often with rounded edges, not exceeding 100 micrometers in size. It rarely forms well-developed, microscopic crystals with cubic or octahedral habits.

Geological environment

## Genesis Atokite is a magmatic mineral. It forms in ultramafic and mafic layered intrusions, in zones rich in platinum-group metal (PGE) sulfides. It crystallizes in the late stages of magmatic processes from residual melts enriched in platinum-group elements and chalcophile elements. ## Mineral Associations This mineral co-occurs with other platinum-group minerals, such as rustenburgite, native platinum, braggite, sperrylite, as well as with base metal sulfides, mainly pentlandite, pyrrhotite, and chalcopyrite. ## Localities The most important and classic locality for atokite is the Atok mine (Bokoni) in the Bushveld Complex in South Africa. Its presence has also been confirmed in other areas of this complex. Outside of South Africa, it has been identified in nickel, copper, and PGE deposits in the Duluth Complex in Minnesota (USA), the Stillwater Complex in Montana (USA), the Lac des Iles deposit in Ontario (Canada), and in some deposits in Russia (Taymyr Peninsula) and Finland.

Rarity

Very rare

For collectors

## Quality Criteria The quality of atokite specimens is assessed primarily from a scientific, rather than aesthetic, perspective. The most valuable samples are those in which atokite grains are relatively large (for this mineral, meaning tens of micrometers), well-separated, and clearly identifiable. The value of a specimen is enhanced by a rich association with other rare platinum-group minerals. These specimens are typically polished sections intended for microscopic examination. ## Popular Localities By far the most prized and historically significant specimens come from the discovery locality – the Atok mine in the Bushveld Complex in the Republic of South Africa. Material from this locality is considered reference material for this mineral.

Care and storage

## Cleaning Atokite specimens, typically in the form of microscopic grains embedded in the host rock, practically do not require cleaning. If dust needs to be removed from the rock matrix, a soft brush or compressed air can be used. All wet and chemical cleaning methods should be avoided. ## What to Avoid Avoid contact with chemicals, especially acids, which can react with the mineral or surrounding sulfides. Although it is a stable mineral, it should not be heated. Store away from humid environments to protect the host rock. ## Storage Specimens containing atokite are best stored under stable conditions, in closed display boxes or mineral cabinets, to protect them from dust and contaminants. Due to the microscopic size of the grains, these specimens often require proper description and marking of the mineral's location on the rock.

Sources

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