Tazieffite

Chemical formula: Pb₂+₂₀Cd₂+₂(As₃+,Bi₃+)₂₂S₂-₅₀Cl₁₀

Tazieffite is an extremely rare lead, cadmium, arsenic, and bismuth sulfide, forming acicular crystals in volcanic fumaroles.

## Characteristics Tazieffite is a complex sulfosalt mineral with a metallic luster and black color. It occurs as very small, acicular crystals, rarely exceeding 1.5 mm in length. These crystals form radial aggregates or chaotic, tangled masses on the surface of volcanic rocks. Due to its chemical composition, containing lead, cadmium, and arsenic, it is a toxic mineral. ## Physical Properties The mineral is characterized by a strong metallic luster and is completely opaque. It has a high density of 6.96 g/cm³, which is typical for lead-rich minerals. Hardness has not been precisely determined. The streak is black. ## Colors and Varieties Tazieffite is monochromatic – it occurs exclusively in black. No color varieties or commercial forms are known. ## History and Name The mineral was approved by the International Mineralogical Association (IMA) in 2003. Its name honors Haroun Tazieff (1914–1998), a French-Belgian volcanologist and geologist, known for his research on active volcanoes and filming documentary movies of eruptions. The discovery was made in the fumaroles of Mutnovsky Volcano in Kamchatka. ## Uses Due to its extreme rarity and microscopic crystal sizes, tazieffite has no industrial applications. It is solely an object of scientific interest and a valuable acquisition for specialized collectors of rare minerals (so-called micromounts).

Properties

Luster: Metallic
Streak: Black
Density: 6.96
Cleavage: None
Transparency: Opaque
Crystal system: Triclinic

Diagnostic features

## Identification Identification of tazieffite is based on a unique set of features: black color, metallic luster, acicular crystal habit forming radial aggregates, and extremely rare occurrence in a specific environment. The key is the place of origin – this mineral is known only from one volcano in the world. Final confirmation requires advanced chemical analyses (e.g., EDS). ## Distinguishing from Similar Minerals Tazieffite can be confused with other black, acicular sulfides or sulfosalts, such as bismuthinite or stibnite. However, it is distinguished by its mineral paragenesis (co-occurrence with kudriavite and cadmoindite) and chemical composition, particularly the simultaneous presence of lead, cadmium, bismuth, arsenic, and chlorine. ## Crystal Forms The mineral forms elongated, acicular crystals up to 1.5 mm long. These crystals often arrange themselves into radial, stellate aggregates or form chaotic, tangled masses resembling felt.

Geological environment

## Genesis Tazieffite forms through sublimation from very high-temperature volcanic gases, estimated at 450–600°C. It crystallizes directly from the gas phase in active fumaroles, which are volcanic exhalations rich in metals and sulfur. ## Mineral Associations This mineral occurs in association with other rare fumarolic minerals. It is most commonly found in association with kudriavite, cadmoindite, and wurtzite. ## Localities The only confirmed locality of tazieffite in the world is its type locality – Mutnovsky Volcano on the Kamchatka Peninsula in Russia.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of tazieffite specimens, which are inherently micromounts, is assessed based on several criteria. Highly valued specimens are those with well-formed, undamaged, acicular crystals forming aesthetic, radial aggregates. The abundance of the mineral on the rock matrix and the presence of well-developed crystals of associated minerals, such as kudriavite, are also important. ## Popular Localities All known collector specimens come from a single location in the world – Mutnovsky Volcano in Kamchatka. This is the only locality from which this mineral is obtained.

Care and storage

## Cleaning Due to its toxic composition (lead, arsenic, cadmium) and delicate structure, extreme caution must be exercised. Specimens should not be wet cleaned. For dust removal, a soft, dry brush or carefully blowing off dust with compressed air from a safe distance can be used. ## What to Avoid Absolutely avoid skin contact with the mineral, and thoroughly wash hands after any contact. Do not inhale dust that might be generated when handling the specimen. The mineral is sensitive to acids. Avoid high temperatures and humidity. ## Storage Tazieffite specimens must be stored in tightly sealed, clearly labeled containers (e.g., "micromount box" type), away from children and pets. It is recommended to keep it in a separate display case or section, isolated from other minerals, to avoid potential contamination of the collection with toxic elements.

Sources

IMA Mineral List (CNMNC)