Clerite

Chemical formula: Mn₂+Sb₃+₂S₂-₄

Clercite is a rare manganese and antimony sulfide, forming acicular crystals with a metallic luster, known only from one deposit in the world.

## Characteristics Clercite is a manganese and antimony sulfide, occurring as very small, acicular or elongated, prismatic crystals. They typically form radial or fan-shaped aggregates. The mineral has a metallic-gray, almost black color and is completely opaque. Individual crystals rarely exceed 1 mm in length, making it a mineral primarily available as microscopic specimens. ## Physical Properties Clercite is characterized by a strong metallic luster. Its density, calculated based on chemical composition and crystal structure, is approximately 4.73 g/cm³. The Mohs hardness has not yet been precisely determined. The mineral is opaque, and its streak is black. ## Colors and Varieties This mineral is monochromatic – it occurs in shades from steel-gray to black. No color varieties or commercial varieties are known. ## History and Name Clercite was recognized as a new mineral species by the International Mineralogical Association (IMA) in 2012. Its name commemorates Onisim Yegorovich Kler (Onésime Clerc, 1845–1920), a Swiss-born Russian naturalist, researcher of the Urals, and long-time director of the Ural Natural History Museum. The mineral was discovered in the Vorontsovskoe gold deposit in the Northern Urals, Russia. ## Applications Due to its extreme rarity and microscopic crystal sizes, clercite has no industrial applications. It is solely an object of scientific interest and is valued by specialized collectors of rare minerals.

Properties

Luster: Metallic
Streak: Black
Density: 4.73
Transparency: Opaque
Crystal system: Orthorhombic

Diagnostic features

## Identification Clercite can be initially identified based on its metallic luster, dark gray color, acicular crystal habit, and characteristic radial aggregates. Its occurrence in association with other antimony minerals in hydrothermal veins is also an important clue. However, definitive identification is almost exclusively possible using advanced analytical methods, such as X-ray microanalysis (EDS/WDS). ## Distinguishing from Similar Minerals This mineral is visually almost impossible to distinguish from other acicular sulfides and sulfosalts, such as stibnite, berthierite, or zinckenite. Stibnite is much softer and exhibits perfect cleavage in one direction. Berthierite has a different chemical composition and often a brownish tint. Final differentiation requires specialized studies. ## Crystal Forms Clercite forms acicular or long-prismatic crystals, which often combine into radial, stellate, or sheaf-like aggregates. Single, well-formed crystals are extremely rare.

Geological environment

## Genesis Clercite forms under low-temperature hydrothermal conditions. It is a component of gold-bearing quartz-carbonate veins, where it crystallizes along with other ore minerals. ## Mineral Associations This mineral occurs in association with other antimony minerals, such as stibnite, berthierite, and native antimony. It also co-occurs with pyrite, arsenopyrite, native gold, quartz, and dolomite. ## Localities The only confirmed locality of clercite in the world is its type locality – the Vorontsovskoe gold deposit, located in the Sverdlovsk Oblast in the Northern Urals, Russia.

Rarity

Very rare

For collectors

## Quality Criteria As a microscopic mineral, the collector value of clercite is assessed differently than for macroscopic specimens. Samples with rich, well-defined aggregates of acicular crystals, clearly visible under magnification, are most highly valued. The aesthetics of associated minerals are also important, especially if gold is present on the specimen. ## Popular Localities All known and commercially available clercite specimens originate from a single location – the Vorontsovskoe gold deposit in the Urals, Russia.

Care and storage

## Cleaning Clercite specimens should only be dry-cleaned, using a soft brush to remove dust. Due to its probable fragility and small crystal sizes, maximum caution should be exercised. Water, and especially chemical cleaning agents, should be avoided. ## What to Avoid As a sulfide, clercite may be sensitive to moisture and oxidation in the long term. It should be protected from contact with acids and other chemicals, as well as from high temperatures and direct sunlight. Cleaning in ultrasonic cleaners is not recommended. ## Storage It is recommended to store specimens in a dry and stable environment, preferably in tightly sealed "micromount" boxes. This will provide protection against mechanical damage, dust, and changes in air humidity.

Sources

IMA Mineral List (CNMNC)