Chvilevaite

Chemical formula: Na(Cu,Fe,Zn)₂S₂

Chvilevaite is a rare sodium, copper, iron, and zinc sulfide, forming tiny, metallic grains in hydrothermal veins.

## Characteristics Chvilevaite is a very rare sulfide mineral, chemically classified as a sodium, copper, iron, and zinc sulfide. It occurs as very fine, anhedral (irregularly shaped) grains, usually not exceeding 0.2 mm in size. These grains are most often intergrown with other minerals, mainly galena. Due to its small size and mode of occurrence, its macroscopic features are difficult to observe without specialized equipment. ## Physical Properties This mineral is characterized by a metallic luster and is opaque. Its Mohs hardness is 3.5. The density calculated based on its chemical composition and unit cell parameters is 4.25 g/cm³. No cleavage has been observed. ## Colors and Varieties Chvilevaite has a creamy-yellow color, which under a microscope in reflected light may exhibit weak pleochroism from creamy-yellow to light pinkish-cream. No varieties have been distinguished. ## History and Name The mineral was first described in 1988 by A.D. Genkin, V.S. Kovalenker, N.V. Troneva, I.P. Laputina, and T.L. Evstigneeva. Its name honors the Russian mineralogist Tatiana Nikiforovna Chvileva (1926–2000), a specialist in ore microscopy, who first discovered this mineral in 1978 but considered it a sodium-rich variety of chalcopyrite. ## Uses Chvilevaite has no practical or industrial significance. Its occurrence is solely of scientific and collector's value for specialized collectors of rare minerals.

Properties

Mohs hardness: 3
Color: Bronze
Luster: Metallic
Streak: Black
Density: 0
Cleavage: on {0001}
Transparency: Opaque
Crystal system: Trigonal

Diagnostic features

## Identification Identification of chvilevaite is impossible without advanced laboratory techniques. Recognition relies on optical analysis in reflected light (characteristic creamy-yellow color and weak pleochroism) and chemical analysis using an electron microprobe (EDS/WDS) to confirm the presence of sodium, copper, iron, zinc, and sulfur in appropriate proportions. ## Distinguishing from Similar Minerals Under the microscope, it can be confused with other sulfides of similar color, such as chalcopyrite, cubanite, or mooihoekite. However, chalcopyrite is distinctly more yellow. Definitive differentiation requires chemical composition analysis, especially confirmation of sodium, which is a key component of chvilevaite. ## Crystal Forms This mineral forms exclusively anhedral (shapeless) grains, often with rounded or irregular outlines. It typically occurs as inclusions in galena, forming intergrowths with it. No euhedral (well-formed) crystals have been observed.

Geological environment

## Genesis Chvilevaite is a mineral of hydrothermal origin. It forms in the late stages of crystallization in quartz-sulfide veins, under low to medium temperature conditions. Its crystallization is associated with metasomatic processes, where sodium-rich fluids interact with previously crystallized sulfides. ## Mineral Associations This mineral most often occurs in paragenesis with galena (often as inclusions), sphalerite, chalcopyrite, pyrite, quartz, dolomite, and calcite. At its discovery locality (Maayak, Russia), it was also accompanied by rare minerals such as mooihoekite and putoranite. ## Localities Chvilevaite is an extremely rare mineral, confirmed in only a few locations worldwide. The type locality is the Maayak copper-nickel deposit in the Norilsk region of Siberia, Russia. Other confirmed occurrences include the Ak-Sug polymetallic deposit in eastern Tuva (Russia) and the Khovu-Aksy deposit, also in the Tuva Republic.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a chvilevaite specimen is determined almost exclusively by the possibility of its identification. Since the mineral occurs as microscopic inclusions, the most valuable specimens are those in which chvilevaite grains are relatively "large" (around 0.1-0.2 mm) and clearly visible against the surrounding matrix (usually galena). The most prized samples are from the type locality (Maayak, Russia), especially those that have been subject to scientific research and have analytically confirmed mineral identity. ## Market Prices Chvilevaite practically does not appear on the open collector's market. Specimens are mainly found in institutional and university collections, as well as among highly specialized "systematic" collectors. Any potential price would be very high and would depend on the quality of analytical confirmation and the abundance of its occurrence in the sample. ## Popular Localities The only source of specimens that can be considered "classic" is the type locality - the Maayak deposit in the Norilsk region of Siberia. Specimens from other, few localities are even rarer.

Care and storage

## Cleaning Due to its extreme rarity, small grain size, and occurrence as inclusions in other minerals (mainly galena), specimens containing chvilevaite should not be cleaned mechanically or chemically. Any attempt at cleaning risks irreversible damage or loss of the mineral. ## What to Avoid Contact with chemicals, acids, and ultrasonic cleaners should be avoided. As a sulfide, it may be sensitive to moisture and oxidation in the long term, which can lead to discoloration and slow decomposition. It should be protected from temperature changes and direct sunlight. ## Storage Specimens containing chvilevaite, typically in the form of polished sections for microscopic examination or fragments of host rock, should be stored under stable conditions. The best solution is a sealed "micromount" box away from dust, moisture, and heat sources to minimize the risk of oxidation.