Chabournéite

Chemical formula: Ag1+zTl1+8-x-zPb2+4+2xSb3+40-x-yAs3+yS2-68 (0.00 ≤ x ≤ 0.40, 16.15 ≤ y ≤ 19.11, 0.04 ≤ z ≤ 0.11)

Chabournéite is a very rare thallium lead antimony arsenic sulfosalt mineral with a metallic luster.

Description

## Characteristics Chabournéite is a very rare, lead-black sulfosalt with a complex chemical composition, containing thallium, lead, antimony, and arsenic. It occurs as fine, anhedral grains or massive aggregates, rarely forming small, tabular or prismatic crystals not exceeding a few millimeters in size. The mineral is opaque and characterized by a strong, metallic luster. ## Physical Properties The Mohs hardness of chabournéite is 3.5, classifying it as a relatively soft mineral. Its density is significant, approximately 5.1 g/cm³, which is noticeable even in small specimens. It has a metallic luster and is completely opaque. ## Colors and Varieties This mineral is monochromatic – it occurs exclusively in black or lead-black color. It does not form color varieties or commercial grades. ## History and Name Chabournéite was first described in 1979 by J. Mantienne. Its name comes from the Chabournéou glacier, located near the type locality – the Jas Roux deposit in the Provence-Alpes-Côte d'Azur region of France. ## Uses Due to its extreme rarity and microscopic occurrences, chabournéite has no industrial applications. It is solely an object of scientific interest and a prized acquisition for specialized collectors of rare minerals and sulfosalts.

Diagnostic features

## Identification Identification of chabournéite is based on its black color, strong metallic luster, relatively high density, and characteristic occurrence environment. Key is its association with other rare thallium sulfosalts, such as pierrotite, and with sulfide minerals like realgar, orpiment, and stibnite. ## Distinguishing from Similar Minerals Visual differentiation of chabournéite from other black, metallic sulfosalts (e.g., pierrotite, baumhauerite, livingstonite) is practically impossible without advanced analytical methods. Certain identification requires chemical analysis, most often using an electron microprobe (EDS/WDS). ## Crystal Forms It most often forms anhedral (irregular) grains embedded in rock or massive, compact aggregates. Well-formed crystals are extremely rare, having a tabular or short-prismatic habit and reaching at most a few millimeters in length.

Geological environment

## Genesis Chabournéite forms as a result of low-temperature hydrothermal processes. It crystallizes in voids and fractures of carbonate rocks, mainly dolomites and dolomitic limestones, in "Carlin-like" deposits or similar As-Sb-Tl mineralizations. ## Mineral Associations This mineral occurs in association with other rare sulfosalts and sulfides. Its typical associations include: pierrotite, parapierrotite, routhierite, stibnite, realgar, orpiment, sphalerite, pyrite, and marcasite. ## Localities The most important and well-known locality for chabournéite is its type locality – Jas Roux in the Hautes-Alpes department of France. This is one of the classic sites of thallium mineralization in the world. Outside of France, its presence has also been reported in the Ab-e-Gaj and Djez-Kassgan deposits in Iran.

Rarity

Very rare

Collector aspects

## Quality Criteria The most highly valued specimens are those that contain even microscopic but well-formed and lustrous chabournéite crystals. The value of a specimen significantly increases when the crystals are set against a contrasting rock matrix or when accompanied by other rare, and especially colorful, minerals such as red realgar or yellow orpiment. ## Popular Localities Undoubtedly, the best and most sought-after chabournéite specimens come from the type locality – Jas Roux in France. Specimens from this location represent the global standard for this mineral.

Care and storage

## Cleaning Specimens should be cleaned only dry, using a soft brush or compressed air to remove dust. Contact with water and all chemical agents, including ultrasonic cleaners, must be strictly avoided. ## What to Avoid Chabournéite contains thallium, which is a highly toxic element. Direct skin contact should be avoided, and hands should be thoroughly washed after handling any specimen. The formation and inhalation of dust must not be allowed. The mineral is sensitive to chemicals. It should also be protected from moisture and extreme temperatures. ## Storage It is recommended to store specimens in closed, dry containers (e.g., "membrane boxes") to limit contact with the environment and prevent accidental dusting. Store away from light, especially if co-occurring with realgar, which is sensitive to UV radiation.