Ferrotorryweiserite

Chemical formula: Rh₅Fe₁₀S₁₆

Ferrotorryweiserite is an extremely rare rhodium and iron sulfide, discovered in river sediments in the Polar Urals, Russia.

## Characteristics Ferrotorryweiserite is a sulfide mineral, an iron (Fe) analog of torryweiserite. It forms microscopic, metallic inclusions up to 150 micrometers in size, most commonly within isoferroplatinum. Its occurrence is limited to single grains in heavy mineral concentrates, thus it does not form macroscopic specimens. It typically occurs as irregular grains or inclusions within other platinum-group minerals. ## Physical Properties This mineral is characterized by a metallic luster and is opaque. Its Mohs hardness is 5. Due to the microscopic size of the grains, other physical properties, such as density or fracture, have not been precisely determined. ## Colors and Varieties Ferrotorryweiserite has a gray color with a reddish tint. No varieties have been distinguished. ## History and Name The name "ferrotorryweiserite" refers to its chemical composition – it is the iron ("ferro") analogue of torryweiserite. It was approved as a new mineral by the International Mineralogical Association (IMA) in 2021 (IMA2021-075). It was described based on material from the Miass River in the Southern Urals, Russia. ## Uses Due to its extreme rarity and microscopic size, ferrotorryweiserite has no practical or commercial applications. It is solely an object of scientific interest and a valuable acquisition for specialized systematic collections.

Properties

Mohs hardness: 5
Luster: Metallic
Transparency: Opaque
Crystal system: Trigonal

Diagnostic features

## Identification Identification of ferrotorryweiserite is impossible without advanced analytical techniques. It requires chemical composition analysis using an electron microprobe (EDS/WDS) and crystallographic studies. In reflected light under a polarizing microscope, it is gray with a reddish tint and exhibits weak anisotropy. ## Distinguishing from Similar Minerals It can be confused with other platinum-group sulfides, such as cuprorhodsite, cuprorhodsite, kingstonite, and especially torryweiserite. Differentiation relies solely on precise analysis of the iron-to-copper ratio in the mineral's structure. ## Crystal Forms Ferrotorryweiserite occurs as anhedral (irregular) grains and inclusions, typically ranging from 5 to 150 micrometers in size. No well-formed crystalline shapes have been observed.

Geological environment

## Genesis Ferrotorryweiserite is a secondary mineral, forming in the oxidation zones of platinum-group mineral deposits. It forms at low temperatures as a result of the alteration of primary sulfides and metal alloys from this group. Its occurrence is associated with alluvial (river) sediments, where it accumulates along with other heavy and resistant minerals. ## Mineral Associations This mineral co-occurs with other platinum-group minerals, such as isoferroplatinum (in which it forms inclusions), osbornite, irarsite, as well as chromite and serpentines. ## Localities The only confirmed locality (type locality) is the alluvial sediments of the Miass River in the Chelyabinsk Oblast, Southern Urals, Russia.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a ferrotorryweiserite specimen depends solely on the confirmation of its presence through chemical analysis. Since it occurs as microscopic inclusions, its visual characteristics, such as color or form, are irrelevant to its collector's value. The most valuable samples are those in which ferrotorryweiserite grains are relatively large (over 100 micrometers) and well-isolated in a polished section, which facilitates their observation and analysis. ## Popular Localities The only source of material from which this mineral was described is river sediments from the Southern Urals in Russia. This mineral is not available on the commercial collector's market.

Care and storage

## Cleaning Specimens containing ferrotorryweiserite (usually as inclusions in other minerals) should only be cleaned with compressed air to remove dust. Any contact with water, and especially with chemicals, is inadvisable. ## What to Avoid Avoid ultrasonic cleaners, chemical agents, acids, and sudden temperature changes. As a sulfide, the mineral may be susceptible to oxidation in a humid environment. ## Storage It is recommended to store specimens in stable, dry conditions, preferably in a sealed, lidded display box to protect them from dust and moisture.

Sources

IMA Mineral List (CNMNC)