Zaykovite

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

Zaykovite is an extremely rare rhodium selenide, occurring as microscopic, metallic grains in sulfide hydrothermal vents.

## Characteristics Zaykovite is a mineral from the sulfide group (although it contains selenium, not sulfur), being a naturally occurring rhodium selenide. It forms extremely small, anhedral (not exhibiting its own crystalline form) grains not exceeding 150 micrometers in size. It occurs as inclusions in other sulfide minerals. Due to its microscopic size, its visual characteristics are observable only under a microscope in reflected light, where it presents a creamy white color with a pinkish hue. ## Physical Properties Due to the extreme rarity and microscopic size of its crystals, most of zaykovite's physical properties have not been fully investigated. Hardness and density have not been measured, but only calculated. The mineral is opaque and exhibits a strong, metallic luster. ## Colors and Varieties The mineral has a constant chemical composition and does not form color varieties. Its color in reflected light is characteristic - creamy white with a pinkish hue. ## History and Name Zaykovite was discovered in samples from the Semenov-2 sulfide field on the Mid-Atlantic Ridge. It was described and approved as a new mineral species by the International Mineralogical Association (IMA) in 2005 (IMA2005-048). The name honors Viktor Vladimirovich Zaykov (1937–2017), a Russian geologist from the Institute of Mineralogy of the Russian Academy of Sciences, for his contributions to the study of sulfide deposits in the Urals. ## Uses Zaykovite has no commercial or industrial applications. Its significance is purely scientific and collectible, as one of the rarest rhodium minerals in the world.

Properties

Luster: Metallic
Streak: Black
Density: 9.45
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of zaykovite is impossible without advanced laboratory techniques. It requires analysis by electron microprobe (EDS/WDS) to confirm its chemical composition (presence of rhodium and selenium). Under a microscope in reflected light, it is characterized by a creamy white color with a pinkish hue and a lack of visible pleochroism or anisotropy. ## Distinguishing from Similar Minerals Due to its occurrence as fine inclusions, it can be confused with many other metallic minerals, such as chalcopyrite, bornite, or other selenides. Definitive differentiation is possible only through chemical analysis. ## Crystal Forms Zaykovite forms only anhedral, irregular grains and aggregates, typically as inclusions in other minerals.

Geological environment

## Genesis Zaykovite forms under specific conditions in submarine hydrothermal vents of the "black smoker" type. It crystallizes from hydrothermal solutions rich in metals, including platinum-group metals, in zones of high sulfide and selenide activity. ## Mineral Associations This mineral occurs in close association with chalcopyrite, bornite, sphalerite, as well as with other rare minerals such as vasilite (Pd,Cu)₁₆(S,Te)₇ and palladseite (Pd₁₇Se₁₅). It typically forms inclusions in chalcopyrite. ## Localities The only confirmed occurrence of zaykovite in the world is its type locality: the Semenov-2 hydrothermal field, located on the Mid-Atlantic Ridge (13°30.83'N, 44°58.72'W).

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a zaykovite specimen is determined solely by its scientific verification. Since the mineral is microscopic, collectible specimens are fragments of the host rock (most often chalcopyrite) with confirmed presence of zaykovite. The most valuable samples are those where zaykovite grains are relatively "large" (over 50 micrometers) and well-isolated, allowing for their observation under a microscope. Analytical documentation (e.g., SEM images, EDS results) should be included with the specimen. ## Popular Localities The only source of specimens is the type locality on the Mid-Atlantic Ridge, which makes them practically unavailable on the commercial market. Specimens are found almost exclusively in institutional and research collections.

Care and storage

## Cleaning Specimens containing zaykovite, usually fragments of sulfide massifs, should not be wet cleaned. Any contaminants should be removed only with a soft brush or compressed air to avoid damaging delicate mineral associations. ## What to Avoid Avoid contact with water, chemicals, acids, and cleaning agents. Sulfide and selenide minerals can oxidize in a humid environment. Also avoid ultrasound and high temperatures. ## Storage Specimens should be stored under stable conditions, in a dry environment, preferably in an airtight container (e.g., a "membrane box" or a box with a desiccant). Protect from dust and direct light.

Sources

IMA Mineral List (CNMNC)