Cuprokalininite

Chemical formula: Cu₁+Cr₃+Cr₄+S₂-₄

Kupokalininite is an extremely rare copper and chromium sulfide, known exclusively from one locality worldwide – Mutnovsky volcano in Kamchatka.

## Characteristics Kupokalininite is a mineral with a metallic luster and black color, occurring as very fine, isometric grains not exceeding 0.2 mm in size. These grains form aggregates or occur as inclusions in other fumarolic minerals, such as kalininite. Due to its extreme rarity and microscopic crystal size, its full visual characterization is limited. ## Physical Properties This mineral is opaque and has a black streak. Its hardness and density have not been precisely measured due to the small amount of available material; however, the density calculated based on its chemical formula and unit cell parameters is 4.31 g/cm³. ## History and Name The name kupokalininite (approved by IMA in 2015, number 2015-012) refers to its chemical composition – it is a copper (*cuprum*) analogue of kalininite, with which it forms a series. It was discovered and described by a team of mineralogists led by Igor V. Pekov based on material collected from fumaroles of the Mutnovsky volcano in Kamchatka, Russia.

Properties

Luster: Metallic
Streak: Black
Density: 4.31
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Cubic

Diagnostic features

## Identification Identification of kupokalininite is possible only through advanced laboratory methods, such as chemical analysis using an electron microprobe (EDS/WDS) and X-ray diffraction (XRD). Visual identification in the field or even under a standard microscope is impossible. ## Differentiation from similar minerals It can be confused with other black, metallic sulfide minerals occurring in the same environment, such as kalininite, cuproiridsite, or malanite. Differentiation requires confirmation of the presence of copper and chromium in its chemical composition. ## Crystal forms Kupokalininite forms very fine, isometric (cubic) crystals up to 0.2 mm in size, which often occur as irregular aggregates or as inclusions within kalininite crystals.

Geological environment

## Genesis Kupokalininite is a mineral of volcanic origin, crystallizing in high-temperature (400-600°C) exhalative fumaroles. It forms as a result of the sublimation of volcanic gases rich in sulfur, copper, and chromium. ## Mineral associations This mineral co-occurs with other rare fumarolic minerals of Mutnovsky volcano, primarily with kalininite (with which it forms a series), as well as wurtzite, sphalerite, galena, chalcopyrite, pyrite, halite, and sylvite. ## Localities The only confirmed locality of kupokalininite worldwide is its type locality – an active fumarole field on the northern slope of Mutnovsky volcano on the Kamchatka Peninsula in Russia.

Rarity

Extremely rare

For collectors

## Quality criteria In the case of such a rare mineral, the only criterion is its confirmed presence in the sample. Specimens have purely scientific value and are of interest to specialized collectors of microscopic minerals (so-called micromounts). Any specimen with confirmed kupokalininite is considered exceptional. ## Popular localities The only source of specimens is Mutnovsky volcano in Kamchatka. Research material is extremely difficult to obtain due to inaccessibility and dangerous conditions in active fumarole fields.

Care and storage

## Cleaning Due to its microscopic size and extreme rarity, kupokalininite specimens are not subjected to standard cleaning. Any manipulation should be performed exclusively under laboratory conditions using a microscope. ## What to avoid Avoid contact with chemicals, moisture, and sudden temperature changes, which could damage the delicate crystals or the host rock. As a mineral formed in a fumarolic environment, it may be unstable under atmospheric conditions. ## Storage Specimens should be stored in specialized, hermetic containers (so-called micromount boxes), protecting them from dust, moisture, and mechanical damage. Storage under stable room conditions is crucial for preserving the integrity of the sample.

Sources

IMA Mineral List (CNMNC)