Lapieite

Chemical formula: Cu₁+Ni₂+Sb₃+S₂-₃

Lapieite is a rare copper, nickel, and antimony sulfide, forming small, metallic grains in serpentinites.

## Characteristics Lapieite is a rare mineral from the sulfide group, composed of copper, nickel, and antimony. It occurs as very small, anhedral (not exhibiting its own crystalline form) grains, usually not exceeding 0.1 mm in size. These grains are disseminated in the host rock, often in association with other ore minerals. Due to its small size, its visual characteristics are difficult to observe without specialized equipment, such as an ore microscope. ## Physical Properties This mineral is characterized by a metallic luster and is opaque. Its Mohs hardness is 5. It is a brittle mineral with an uneven fracture. Cleavage has not been observed. The density calculated based on its chemical composition and unit cell parameters is 5.43 g/cm³. ## Colors and Varieties In reflected light (under a microscope), lapieite is gray with a pinkish tint. No color or commercial varieties are distinguished. ## History and Name Lapieite was discovered and described in 1983 by D.C. Harris, A.C. Roberts, R.I. Thorpe, A.J. Criddle, and C.J. Stanley. The mineral's name comes from its discovery location along the Lapie River in Canada's Yukon Territory. This is the only confirmed occurrence of this mineral in the world (as of 2023). ## Applications Lapieite has no industrial applications. Its significance is purely scientific and collectible, as a unique and rare component of ore parageneses in serpentinites.

Properties

Mohs hardness: 5
Luster: Metallic
Streak: Black
Density: 5.43
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Orthorhombic

Diagnostic features

## Identification Identification of lapieite is impossible with the naked eye and requires advanced laboratory techniques. The primary method is analysis in reflected light under a polarizing microscope (ore microscope), which allows observation of its characteristic color, anisotropy, and co-occurrence with other sulfides. Final confirmation of identity requires chemical analysis using an electron microprobe (EDS/WDS) or X-ray diffraction (XRD). ## Distinguishing from Similar Minerals Under the microscope, lapieite can be confused with other sulfides of a similar hue, such as pentlandite, gersdorffite, or ullmannite. Differentiation is based on precise measurements of light reflectance (reflectivity) and chemical composition analysis, which for lapieite is unique (a combination of Cu, Ni, and Sb). ## Crystal Forms Lapieite forms only very fine, irregular, anhedral grains disseminated in the rock. No well-formed crystals have been observed.

Geological environment

## Genesis Lapieite forms as a result of hydrothermal processes occurring within serpentinized ultramafic rocks (serpentinites). Its crystallization is associated with low-temperature solutions rich in sulfur, antimony, nickel, and copper, which migrate through fractures in the rock. ## Mineral Associations This mineral occurs in close association with other sulfides and arsenides. It is most commonly accompanied by: pentlandite, heazlewoodite, nickeline, maucherite, gersdorffite, ullmannite, chalcopyrite, digenite, djurleite, chalcocite, as well as magnetite and awaruite. It also co-occurs with minerals from the chlorite group, such as clinochlore. ## Localities The only known and confirmed occurrence of lapieite in the world is its type locality along the Lapie River, in the Mayo mining district, Yukon Territory, Canada.

Rarity

Extremely rare

For collectors

## Quality Criteria Due to its extreme rarity and microscopic size, the collectible value of lapieite is not assessed based on typical criteria such as color or form. The most valuable are rock specimens (so-called "micromounts") from the type locality, in which the presence of lapieite has been confirmed by analyses. The value of a specimen is enhanced by a rich association with other rare nickel sulfides and arsenides. ## Popular Localities The only source of lapieite specimens is its discovery site in Yukon, Canada. Material from this locality is extremely difficult to obtain and appears on the collector's market sporadically, mainly circulating among specialized rare mineral collectors and scientific institutions.

Care and storage

## Cleaning Due to the extremely small size of the grains and their occurrence within the host rock, isolated cleaning of individual lapieite specimens is practically impossible and unnecessary. Any cleaning pertains to the entire rock and should be limited to gently wiping with a dry, soft brush to remove dust. ## What to Avoid Contact with chemicals, especially acids, which can react with sulfides, should be avoided. Rock containing lapieite should be protected from moisture to prevent oxidation of associated sulfide minerals. The specimen should not be subjected to ultrasound or rapid temperature changes. ## Storage Rock specimens with lapieite are best stored in stable room conditions, in a dry place, away from direct sunlight. It is recommended to place them in sealed "micromount" boxes, which protect against dust and mechanical damage.

Sources

IMA Mineral List (CNMNC)