Arzakite

Chemical formula: Hg<sub>3</sub>S<sub>2</sub>(Br,Cl)<sub>2</sub>

Arzakite is a rare mercury sulfide and halide, forming tiny, red to reddish-orange crystals and aggregates.

## Characteristics Arzakite is a mineral from the sulfide and halide group, chemically a complex mercury sulfide and halide. It occurs as very small, tabular or prismatic crystals, rarely exceeding 0.5 mm. Most often, it forms granular, earthy, or powdery aggregates and coatings. Its intense, red to reddish-orange color is one of its most characteristic visual features. ## Physical Properties Arzakite crystals exhibit an adamantine luster, while its earthy aggregates are dull. It is a relatively soft mineral, with a Mohs hardness of approximately 2. Due to its mercury content, it has a high density, around 7.7 g/cm³. It is opaque or at most translucent on thin edges. ## Colors and Varieties This mineral occurs in characteristic shades of red: from bright red, through reddish-orange, to reddish-brown. Its streak is light orange. No named varieties of this mineral are distinguished. ## History and Name Arzakite was discovered in the Arzak deposit in the Republic of Tuva, Russia, and described in 1987 by V.I. Vasil'ev, N.A. Pal'chik, and O.K. Grechishchev. The mineral's name comes directly from its discovery location (type locality). ## Uses Due to its extreme rarity and small crystal size, arzakite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals or mercury minerals.

Properties

Mohs hardness
2
Luster
Adamantine
Streak
Light orange
Density
7.7
Cleavage
Perfect on {100}
Fracture
Uneven
Transparency
Translucent to Opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Key diagnostic features of arzakite include its intense red or reddish-orange color, light orange streak, high density, and association with other mercury minerals. The adamantine luster of well-formed crystals, though rare, is also helpful for identification. ## Distinguishing from Similar Minerals Arzakite can be confused with cinnabar (HgS), with which it often co-occurs. Cinnabar has a similar color and hardness but usually forms better-developed, larger crystals and has a slightly different, red streak. Distinguishing it from other red mercury minerals, such as korderoite, may require advanced analytical methods (e.g., EDS/XRD). ## Crystal Forms Arzakite crystallizes in the monoclinic system. It forms very small, tabular or short-prismatic crystals. It is most commonly found in the form of fine-grained, earthy, or powdery aggregates, as well as coatings on other minerals.

Geological environment

## Genesis Arzakite is a low-temperature hydrothermal mineral. It forms in the oxidation zones of mercury-antimony deposits, often as a result of the alteration of other mercury minerals, such as cinnabar. ## Mineral Associations This mineral co-occurs with other mercury minerals and ore minerals. It is most commonly associated with: cinnabar, native mercury, korderoite, calomel, eglestonite, kuznetsovite, as well as quartz, calcite, baryte, and stibnite. ## Localities The most important and type locality for arzakite is the Arzak deposit in the Republic of Tuva, Russia. It has also been identified in small quantities in several other locations worldwide, including the Khaidarkan deposit in Kyrgyzstan and the Terlingua mines in Texas, USA.

Rarity

Very rare

For collectors

## Quality Criteria The most desirable specimens for collectors are those with visible, even microscopic, well-formed arzakite crystals of intense red color. Rich aggregates and coatings of vivid color, contrasting with the host rock (matrix), most often quartz, are also highly valued. Due to its rarity, any documented specimen has collector's value. ## Popular Localities By far the most prized and classic specimens come from the type locality - the Arzak deposit in Russia. Material from this site is considered exemplary for this mineral species.

Care and storage

## Cleaning Due to its fragility and potential toxicity, mechanical cleaning is highly inadvisable. If absolutely necessary, compressed air can be used to remove dust. Avoid contact with water and chemicals. ## What to Avoid Arzakite is a mercury-containing mineral, which is toxic. Inhaling dust and direct skin contact must be strictly avoided. It should not be heated, as this can lead to the release of toxic mercury vapors. Protect it from acids and other chemicals. ## Storage Arzakite specimens must be stored in tightly sealed, clearly labeled containers (e.g., "perky box" type), away from children and pets. Store in a dry place, away from sunlight and heat sources. It is recommended to wash hands after any contact with the mineral.

Sources

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