Cuproiridsite

Chemical formula: Cu₁+Ir₃+Ir₄+S₂-₄

Cuproiridsite is a very rare, metallic mineral from the thiospinel group, containing copper and iridium.

## Characteristics Cuproiridsite is a mineral from the thiospinel group, occurring as very small, rounded grains or inclusions in other minerals, mainly in platinum-group element alloys. These grains rarely exceed 0.1 mm in diameter. In reflected light, its color is gray with a pinkish hue. ## Physical Properties As an opaque mineral with a metallic luster, cuproiridsite is characterized by high density, resulting from the presence of heavy iridium. It is a hard mineral, which is typical for platinum-group metal sulfides. ## Colors and Varieties This mineral is uniform in composition and does not form color varieties. Its color is constant - steel-gray to black, with a pinkish hue visible under the microscope. ## History and Name Cuproiridsite was first described in 1969 by D.C. Harris and D.P. Cox. Its name comes from its chemical composition - copper (Latin: *cuprum*) and iridium (*iridium*). Type specimens originate from the ultramafic massif on Unst Island in the Shetland Islands, Scotland. ## Applications Cuproiridsite has no industrial application due to its extreme rarity and microscopic size. It is of purely scientific significance and is an object of interest for specialized collectors of microscopic minerals.

Properties

Mohs hardness: 5
Luster: Metallic
Streak: Black
Density: 9.55
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Cubic

Diagnostic features

## Identification Identification of cuproiridsite is impossible without specialized equipment. It requires analysis under a petrographic microscope in reflected light and confirmation of chemical composition using an electron microprobe (EDS/WDS). Its characteristic feature is a pinkish hue against a gray background. ## Distinguishing from Similar Minerals It can be confused with other platinum-group element sulfides, such as malanite (which is darker and has a weaker hue) or cuprorhodsite. Definitive differentiation is only possible based on chemical analysis. ## Crystal Forms Cuproiridsite forms only microscopic, rounded or irregular grains. Well-formed crystals are not observed.

Geological environment

## Genesis Cuproiridsite is a mineral of magmatic origin. It crystallizes in ultramafic igneous rocks, such as dunites and peridotites, through the segregation of sulfides from magma rich in platinum-group elements (PGE). ## Mineral Associations It most commonly co-occurs with other platinum-group minerals, such as laurite, irarsite, osmiridium, as well as chromite, chalcopyrite, bornite, and pyrite. ## Localities The most important confirmed localities worldwide include Unst Island (Shetland Islands, Scotland - type locality), Nizhny Tagil massif (Urals, Russia), Bushveld Complex (South Africa), Yubdo district (Ethiopia), and some deposits in Colombia and Canada.

Rarity

Extremely rare

For collectors

## Quality Criteria In the case of cuproiridsite, the only criteria are certainty of identification and the richness of the mineral association on the sample. Specimens on which several different, rare platinum-group minerals can be observed together are most valued. The size of cuproiridsite grains is secondary, as they are always microscopic. ## Popular Localities The most sought-after specimens by specialized collectors come from classic localities such as the Russian Urals (Nizhny Tagil) and South Africa (Bushveld Complex), which yield rich associations of PGE minerals.

Care and storage

## Cleaning Cuproiridsite specimens are typically microscopic inclusions in host rock or polished samples for study (so-called "polished sections"). They do not require and should not be subjected to cleaning under household conditions. Any dirt can only be removed with compressed air. ## What to Avoid Avoid contact with chemicals, acids, and ultrasound, which can damage both the mineral itself and the surrounding rock. The specimen should not be heated. ## Storage Microscopic specimens are best stored in special "micromount" boxes, protecting them from dust and mechanical damage. Polished sections should be stored in a dry place, in designated containers.

Sources

IMA Mineral List (CNMNC)