Kuliginite

Chemical formula: Fe<sup>2+</sup><sub>3</sub>Mg(OH)<sub>6</sub>Cl<sub>2</sub>

Kuliginite is a very rare iron and magnesium hydroxychloride, forming tiny, hexagonal plates with a metallic luster.

## Characteristics Kuliginite is a mineral from the hydroxychloride group, chemically classified as an iron and magnesium hydroxychloride. It occurs as very small, hexagonal, platy crystals, rarely exceeding 0.2 mm. It typically forms thin, rosette-like or scaly aggregates on the surface of other minerals. Its dark brown to almost black color and metallic luster are characteristic of this mineral. ## Physical Properties Kuliginite is characterized by a metallic luster and is opaque. Its Mohs hardness is approximately 2, making it a very soft mineral. The density calculated from its chemical formula and unit cell parameters is 3.05 g/cm³. The mineral exhibits perfect cleavage in one plane, consistent with its platy structure. ## Colors and Varieties This mineral is dark brown to black, and in transmitted light, its very thin plates may show a color ranging from reddish-brown to greenish-brown. No named varieties of kuliginite have been distinguished. ## History and Name Kuliginite was discovered in the Oktyabrsky nickel-copper mine, in the Norilsk region of Siberia, Russia. It was described and approved as a new mineral species by the International Mineralogical Association (IMA) in 2005. Its name honors the Polish geologist Stanisław Kulig (1927-1996), who made significant contributions to geological research on ore deposits in the Norilsk region. ## Uses Due to its extreme rarity and microscopic crystal size, kuliginite has no industrial applications. It is solely an object of scientific and collecting interest for specialized collectors of rare minerals.

Properties

Mohs hardness
2
Luster
Metallic
Streak
Brown
Density
3.05
Cleavage
Perfect on {0001}
Fracture
Micaceous
Transparency
Opaque
Crystal system
Trigonal

Diagnostic features

## Identification Identifying kuliginite under amateur conditions is practically impossible. Identification requires advanced analytical methods, such as X-ray diffraction (XRD) and chemical analysis using an electron microprobe (EDS/WDS). Visually, it can be suspected based on its form (tiny, hexagonal plates), dark color, metallic luster, and co-occurrence with characteristic minerals in its type locality. ## Distinguishing from Similar Minerals Kuliginite can be confused with other small, platy, dark minerals, such as hematite, magnetite, or some micas (e.g., biotite). Differentiation is based on chemical analysis – kuliginite is the only one of these that is an iron and magnesium hydroxychloride. Its perfect cleavage and very low hardness can be helpful in distinguishing it from harder iron oxides. ## Crystal Forms Kuliginite forms thin, tabular or platy crystals with a hexagonal outline. They usually occur as small, rosette-like or scaly aggregates.

Geological environment

## Genesis Kuliginite forms as a result of hydrothermal processes within copper-nickel sulfide deposits. It crystallizes in the late stages of mineralization, forming in fractures and voids within gabbro-dolerite rocks that have been altered by hydrothermal solutions. ## Mineral Associations This mineral occurs in association with other rare secondary minerals. In its type locality (Oktyabrsky mine), it was found in association with goethite, magnesium chlorite, saponite, quartz, calcite, sulfides (chalcopyrite, pentlandite, bornite), and other rare hydroxide minerals, such as iowaite. ## Localities The only confirmed and described occurrence of kuliginite in the world is its type locality – the Oktyabrsky mine, within the Talnakh deposit, near Norilsk, on the Putorana Plateau, Siberia, Russia.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a kuliginite specimen is primarily determined by the abundance and visibility of crystals on the rock matrix. The most desirable specimens are those with clearly formed, though still microscopic, rosettes or aggregates of platy crystals. Contrast with a light matrix (e.g., calcite or quartz) also enhances visual appeal. Due to its microscopic nature, the quality of accompanying photomicrography is crucial. ## Popular Localities The only source of kuliginite specimens is the Oktyabrsky mine in the Norilsk region of Russia. All specimens available on the collector's market originate from this single location.

Care and storage

## Cleaning Kuliginite specimens are extremely delicate and usually microscopic. Mechanical or chemical cleaning is not recommended. If absolutely necessary, compressed air (from a safe distance) can be used to remove loose dust particles. ## What to Avoid Avoid contact with water, acids, and any chemical agents that may react with chlorides or hydroxides. The mineral is very soft, so it should be protected from any physical contact and scratching. It should not be heated or exposed to ultrasound. ## Storage Kuliginite specimens should be stored exclusively in specialized "micromount" boxes, protecting them from dust, moisture, and mechanical damage. Avoid humidity fluctuations, which could harm the mineral.

Sources

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