Kolymite

Chemical formula: Cu<sub>₇</sub>Hg<sub>₆</sub>

A natural amalgam of copper and mercury, a very rare mineral occurring as fine, metallic grains.

## Characteristics Kolymite is a natural alloy (amalgam) of copper and mercury. It most commonly occurs as very small, anhedral (irregular) grains up to 0.5 mm in size, as well as coatings on native gold grains or in dendritic (tree-like) aggregates. It is an opaque mineral with a strong, metallic luster. Fresh surfaces are creamy white or yellowish-cream, but they quickly dull and become covered with a gray or black tarnish upon exposure to air. ## Physical Properties Kolymite is characterized by a very high density, exceeding 12 g/cm³, which is noticeable even in small samples. Its Mohs hardness is approximately 4. It does not exhibit cleavage. Due to its chemical composition, it is a toxic mineral. ## Colors and Varieties The typical color of kolymite is creamy white, sometimes with a yellowish or grayish tint. No distinct color varieties or commercial varieties are recognized. The change in color to dark gray or black is a result of the mineral's surface oxidation. ## History and Name The mineral's name comes from the Kolyma River in Siberia, Russia, where it was first found and described. It was approved as a new mineral species in 1980 by a team of Russian researchers: E. A. Markova, N. M. Chernitsova, J. S. Borodayev, L. S. Dubakina, and O. E. Yushko-Zakharova. ## Uses Kolymite has no industrial applications. Its significance is purely scientific and as a collector's item, due to its extreme rarity and specific chemical composition.

Properties

Mohs hardness: 4
Luster: Metallic
Density: >12
Cleavage: None
Transparency: Opaque
Crystal system: Isometric

Diagnostic features

## Identification Key diagnostic features of kolymite include its creamy white color, strong metallic luster, very high density, and tendency to tarnish quickly. Its occurrence in association with native gold, cinnabar, and other mercury minerals is a strong indicator. Due to the small size of the grains, definitive identification almost always requires advanced analytical methods, such as X-ray microanalysis (EDS/WDS). ## Distinguishing from Similar Minerals Kolymite can be confused with other natural amalgams, such as moschellandsbergite (silver amalgam) or belendorffite (another copper amalgam). Distinguishing it from these is practically only possible through chemical analysis. It may also resemble some native metals, such as platinum or silver, from which it differs in hardness and specific associated minerals. ## Crystal Forms Kolymite primarily forms irregular, rounded grains. It is also found in dendritic aggregates and as thin coatings on other minerals, especially gold. Well-formed crystals are extremely rare.

Geological environment

## Genesis Kolymite is a hydrothermal mineral. It forms at low temperatures in ore deposits rich in mercury, gold, silver, and antimony. Secondarily, it can be found in placer deposits, which formed as a result of erosion and weathering of primary parent rocks. ## Mineral Associations This mineral most commonly co-occurs with native gold, native mercury, cinnabar, metacinnabar, stibnite, potarite, kuznetsovite, and shakhovite. ## Localities The most important and classic locality for this mineral is the Krokhalinnoye deposit in the Kolyma River basin (Magadan Oblast, Russia). It is also known from several other Russian localities (e.g., the Galkhaya deposit in Yakutia) and from placer deposits in Alaska, USA (including the Tofty and Goodnews Bay areas).

Rarity

Very rare

For collectors

## Quality Criteria The quality of kolymite specimens, which are usually microminerals, is primarily assessed based on the abundance of its occurrence on the rock matrix and the clarity of its association with other rare minerals, especially gold. Specimens with visible dendritic aggregates or distinct coatings are most prized. Any specimen with a form even partially resembling a crystal is considered exceptional. ## Popular Localities The most classic and sought-after specimens by collectors come from the type locality in Russia (Magadan Oblast). Material from this region is considered reference for this species.

Care and storage

## Cleaning This mineral is very sensitive and toxic. Generally, it should not be wet cleaned. If necessary, a very soft brush can be used to remove loose contaminants or compressed air from a safe distance. ## What to Avoid **Caution: Toxic mineral!** Contains mercury, which is highly poisonous. Avoid skin contact, and especially avoid inhaling dust. Wash hands thoroughly after each contact with the specimen. Kolymite tarnishes easily in air, so limit its contact with moisture and oxygen. Do not heat it, as this leads to the release of toxic mercury vapors. ## Storage Kolymite specimens must be stored in airtight, sealed containers (e.g., perky boxes) to prevent oxidation and reduce the risk of mercury exposure. The container should be clearly labeled as toxic. Store away from other minerals that may react with mercury vapors.

Sources

IMA Mineral List (CNMNC)