Kingstonite

Chemical formula: Rh<sub>₃</sub>S<sub>₄</sub>

An extremely rare rhodium sulfide, known only from a single microscopic grain found in Ethiopia.

## Characteristics Kingstonite is a mineral with a metallic luster and a dark gray color. It is opaque. It was described based on a single, anhedral (irregular) grain measuring only 120 x 140 micrometers, making it one of the rarest minerals on Earth. Due to its microscopic size, its visual characteristics cannot be assessed with the naked eye. ## Physical Properties The mineral is characterized by a calculated density of 7.33 g/cm³. Its hardness has not been determined due to the lack of sufficient material for testing. It has a black streak and a metallic luster. ## Colors and Varieties The observed color is dark gray. No varieties of this mineral have been distinguished. ## History and Name Kingstonite was recognized as a new mineral in 1993. Its name honors Gordon Kingston, a lecturer in geology at the Royal School of Mines in London, in recognition of his contributions to the study of platinum-group element (PGE) mineralogy.

Properties

Luster: Metallic
Streak: Black
Density: 7.33
Transparency: Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of kingstonite is impossible without advanced analytical techniques, such as X-ray microanalysis (EDS/WDS) in an electron microscope. Visual characteristics, such as metallic luster and gray color, are non-specific. ## Distinguishing from Similar Minerals Visually, it is indistinguishable from many other sulfides and platinum-group metal alloys that form similar microscopic, metallic grains. Definitive differentiation requires chemical composition analysis. ## Crystal Forms It is known exclusively in the form of a single, irregular (anhedral) grain. No well-formed crystal faces have been observed.

Geological environment

## Genesis Kingstonite was found as a single grain in alluvium (river sediments), meaning it was washed out from its primary host rock. It is presumed that this rock was dunite, an ultramafic igneous rock. ## Mineral Associations The only known grain of kingstonite occurred as an inclusion in an osmium-iridium-ruthenium (Os-Ir-Ru) alloy, which is its key associated mineral at the discovery site. ## Localities The only confirmed locality in the world is the alluvium of the Bir Bir River in the Yubdo district (Oromia), Ethiopia. This is the type locality for this mineral.

Rarity

Extremely rare

For collectors

## Quality Criteria Since this mineral is known from a single microscopic grain, it does not exist on the collector's market. The only known material is part of scientific collections (likely at the Natural History Museum in London). Its value is purely scientific. ## Popular Localities No collector specimens exist. The only source is the type locality in Ethiopia, from which the research material originates.

Care and storage

## Cleaning Specimens of this mineral, being microscopic grains, are typically scientific preparations (so-called "micromounts") and should not be cleaned in any way. Any attempt at cleaning risks irreversible loss or damage to the material. ## What to Avoid All shocks, vibrations, contact with chemicals, and attempts at physical manipulation. It should be protected from dust and moisture. ## Storage Store exclusively in a dedicated, tightly sealed "micromount" box, under stable temperature and humidity conditions, away from sources of vibration.

Sources

IMA Mineral List (CNMNC)