Arsenohauchecornite

Chemical formula: Ni₁₈Bi₃AsS₁₆

Arsenohauchecornite is a rare nickel, bismuth, and arsenic sulfide, forming metallic, tabular crystals with a brownish luster.

## Characteristics Arsenohauchecornite is a very rare mineral from the sulfide group, being the arsenic analog of hauchecornite. It forms small, tabular or short prismatic crystals, often with a square cross-section, reaching sizes up to several millimeters. It usually occurs as inclusions in other sulfides. Its appearance is metallic, opaque, with a color ranging from light brownish-brown to tin-white with a pinkish tint. ## Physical Properties This mineral is characterized by a Mohs hardness of approximately 5. It has a metallic luster and is opaque. Its density is high, calculated at 6.55 g/cm³. The streak is black. It does not exhibit cleavage, and its fracture is uneven. ## History and Name The name "arsenohauchecornite" refers to its chemical composition – the dominance of arsenic – and its relationship to the structurally similar mineral, hauchecornite. It was first described in 1980 by D.C. Harris, D.R. Owens, and J.M. Duke based on material from the Vermilion mine in the Sudbury district, Ontario, Canada.

Properties

Mohs hardness: 5
Luster: Metallic
Streak: Black
Density: 6.55
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Tetragonal

Diagnostic features

## Identification Identifying arsenohauchecornite in practice is extremely difficult without advanced analytical methods. Preliminary identification is based on its metallic luster, brownish color, tetragonal crystal form, and co-occurrence with other nickel and copper sulfides. Definitive identification requires chemical analysis (e.g., EDS) to confirm the presence of nickel, bismuth, arsenic, and sulfur in appropriate proportions. ## Distinguishing from Similar Minerals It can be confused with other rare sulfides and arsenides with a metallic luster, such as hauchecornite, pentlandite, gersdorffite, or nickeline. Hauchecornite is practically indistinguishable visually and requires chemical analysis (it contains antimony instead of arsenic). Other minerals differ subtly in color, hardness, or crystal form, but a definitive distinction is almost exclusively possible through laboratory methods. ## Crystal Forms Crystals are usually small, tabular or short prismatic, often exhibiting a square outline. They occur as single, well-formed crystals or inclusions within other ore minerals.

Geological environment

## Genesis Arsenohauchecornite is a hydrothermal mineral. It forms in nickel and copper sulfide deposits, often associated with intrusions of igneous rocks such as gabbro and norites. It forms in the late stages of crystallization from solutions rich in nickel, bismuth, arsenic, and sulfur. ## Mineral Associations This mineral co-occurs with other sulfides and arsenides. It is most commonly associated with chalcopyrite, pentlandite, millerite, gersdorffite, nickeline, maucherite, as well as platinum-group minerals (PGM) and native gold. ## Localities The most important and well-documented arsenohauchecornite localities worldwide include: - Vermilion Mine in the Sudbury district, Ontario, Canada (type locality). - Oktyabrskoye nickel deposit, Norilsk region, Siberia, Russia. - Meskänttö Mine, Nivala deposit, Finland.

Rarity

Very rare

For collectors

## Quality Criteria Due to its extreme rarity, every analytically confirmed arsenohauchecornite specimen is valuable for specialized systematic collections and micromounts. Specimens with visible, well-formed crystals are most highly prized, even if they are microscopic in size. Precise locality information and documented analysis confirming the mineral's identity are crucial. Contrast with the surrounding matrix (e.g., with chalcopyrite) enhances aesthetic value. ## Popular Localities The most sought-after specimens by collectors come from the type locality, the Vermilion mine in Canada, and from the deposit in the Norilsk region of Russia, where well-formed microcrystals are known.

Care and storage

## Cleaning Due to its extreme rarity and occurrence as small inclusions, mechanical cleaning of specimens is usually neither necessary nor advisable. If absolutely essential, compressed air can be used to remove dust. Avoid contact with water and chemicals. ## What to Avoid Avoid all acids and strong chemicals that can react with sulfides. The mineral is sensitive to oxidation, so it should be protected from moisture and sudden temperature changes. Do not subject it to ultrasonic cleaning. ## Storage Specimens with arsenohauchecornite should be stored under stable conditions, preferably in closed, dry containers or display cases with controlled humidity, to prevent oxidation processes. They should be protected from dust and mechanical damage.

Sources

IMA Mineral List (CNMNC)