Auerbakhite

Chemical formula: Mn₂+Tl₁+₂As₃+₂S₂-₅

Auerbachite is an extremely rare manganese and thallium sulfarsenide, forming small, metallic, dark gray crystals.

## Characteristics Auerbachite is a sulfosalt mineral, distinguished by its complex chemical composition including manganese, thallium, and arsenic. It occurs as very small, tabular or bladed crystals, typically not exceeding 0.3 mm in length. It is also observed in aggregates and intergrowths with other rare minerals. Its crystals are dark gray, almost black, and exhibit a strong, metallic luster. ## Physical Properties This mineral is characterized by a metallic luster and is opaque. Its hardness and density have not been precisely measured due to its extreme rarity and small crystal size. The streak is reddish-brown. ## History and Name The mineral is named in honor of the Russian mineralogist and collector Dmitry Vladimirovich Auerbach (1936–2019) in recognition of his contributions to the study of Ural deposits. Auerbachite was approved as a new mineral species by the International Mineralogical Association (IMA) in 2020 (IMA2020-034). It was discovered in volcanic exhalation products (fumaroles) at Tolbachik volcano in Kamchatka, Russia.

Properties

Luster: Metallic
Streak: Red-brown
Transparency: Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of auerbachite is only possible using advanced analytical methods, such as energy-dispersive spectroscopy (EDS) in a scanning electron microscope (SEM) or X-ray diffraction (XRD). Under collecting conditions, identification is impossible. A characteristic feature in analysis is the unique combination of manganese, thallium, and arsenic as main components. ## Differentiation from similar minerals It can be confused with other fine-crystalline, metallic sulfosalts occurring in the same environment, such as kutinaite, pierrotite, or rebulite. Differentiation requires specialized chemical analysis. ## Crystal forms It forms very small, flattened, tabular or bladed crystals, often grouped into small aggregates.

Geological environment

## Genesis Auerbachite is a mineral of volcanic origin, crystallizing from gases (exhalations) in fumaroles. It forms in zones with temperatures around 100-120°C as a result of the sublimation of components brought up from deep within the volcano. ## Mineral associations It co-occurs with other rare fumarolic minerals, such as realgar, orpiment, kutinaite, and native sulfur. ## Localities The only confirmed locality in the world is the Yadovitaya fumarole on the second cone of the North Breach of the Great Fissure Eruption of Tolbachik volcano on the Kamchatka Peninsula in Russia.

Rarity

Extremely rare

For collectors

## Quality criteria As a "micromount" type mineral, the collector's value of auerbachite primarily depends on laboratory confirmation of its identity. The most desirable specimens are those with the largest possible, well-formed crystals, clearly visible under a microscope and set on a contrasting matrix. The presence of associated minerals can increase the value of the specimen. ## Popular localities The only source of specimens is its type locality - Tolbachik volcano in Kamchatka, Russia. Material from this location is extremely difficult to acquire.

Care and storage

## Cleaning Due to its extreme rarity, small size, and potential toxicity (thallium and arsenic content), auerbachite specimens should not be cleaned under amateur conditions. All conservation activities should be left to specialized laboratories. ## What to avoid Any contact with water, chemicals, ultrasound, and abrasion should be avoided. The mineral is likely sensitive to changes in temperature and humidity. Due to its thallium and arsenic content, inhalation of dust and direct skin contact must be strictly avoided. ## Storage Specimens should be stored exclusively in specialized, sealed "micromount" containers, away from light, moisture, and vibrations. It is essential to clearly label the mineral as toxic.

Sources

IMA Mineral List (CNMNC)