Fleetite

Chemical formula: Cu<sub>2</sub>RhIrSb<sub>2</sub>

Fleetite is a very rare sulfide of copper, rhodium, iridium, and antimony, identified from a single grain.

## Characteristics Fleetite is an extremely rare mineral from the sulfosalt group, identified from a single, anhedral (irregularly shaped) grain approximately 1.4 x 1.0 mm in size. This grain was intergrown with other similarly rare minerals. In reflected light, fleetite is gray to white in color. ## Physical Properties Due to the size and nature of the only known specimen, most physical properties, such as hardness, density, luster, or fracture, have not been determined. The mineral is opaque. ## History and Name Fleetite was officially recognized by the International Mineralogical Association (IMA) in 2018 under number IMA2018-058. The name honors Professor Michael E. Fleet (born 1938) from the University of Western Ontario in Canada, in recognition of his significant contributions to mineralogy, crystal chemistry, and geochemistry, especially in the study of platinum-group minerals (PGM) and sulfides.

Properties

Luster
Metallic
Transparency
Opaque
Crystal system
Cubic

Diagnostic features

## Identification Identification of fleetite is possible only through advanced laboratory techniques, such as X-ray microanalysis (EDS/WDS) combined with X-ray diffraction or electron backscatter diffraction (EBSD), to determine its chemical composition and crystal structure. Visual properties are not sufficient for identification. ## Distinguishing from Similar Minerals This mineral occurs in complex intergrowths with other sulfides and sulfosalts of platinum-group metals, such as irarsite, hollingworthite, or platarsite. Distinguishing it from these requires precise analysis of the chemical composition, especially the proportions between rhodium, iridium, platinum, and antimony. ## Crystal Forms The only known specimen is a single, anhedral (irregularly shaped) grain. Crystal forms are not known.

Geological environment

## Genesis Fleetite formed as a result of hydrothermal processes within ultramafic rocks. Its presence is associated with the concentration of platinum-group elements (PGE) in magmatic deposits. ## Mineral Associations The type mineral was found in paragenesis with chromite, laurite, irarsite, hollingworthite, platarsite, Os-Ir-Ru alloys, and an undetermined Rh-Ir-Ni-Cu sulfide. ## Localities The only confirmed worldwide occurrence (type locality) is the ultramafic rock complex in Onverwacht, near Steelpoort, South Africa. This is a historic platinum mine from which many rare PGM minerals originated.

Rarity

Extremely rare

For collectors

## Quality Criteria As a mineral of purely scientific significance, fleetite is not available on the collector's market and is not subject to quality assessment in the traditional sense. The scientific value of a specimen lies in its existence and the possibility of studying its composition and structure.

Care and storage

## Cleaning Due to its extreme rarity and small size, fleetite specimens should not be cleaned under amateur conditions. Any treatments should be left to specialized research laboratories. ## What to Avoid Avoid any contact with chemicals, ultrasonics, temperature changes, and any mechanical manipulations that could irreversibly damage or destroy the only known material. ## Storage The only known material is stored under archival conditions in a scientific institution. Any potential new material should be stored under stable conditions, in a specialized container, away from vibrations, moisture, and contaminants.

Sources

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