Jinxiuite

Chemical formula: Ni₁₈Bi₂SbAsS₁₆

Jinxiuite is an extremely rare, metallic, steel-gray mineral, which is a complex nickel, bismuth, antimony, and arsenic sulfide.

## Characteristics Jinxiuite is a very rare mineral from the sulfide group, identified only in 2023. It occurs as anhedral (irregular) grains up to 200 micrometers in size, usually intergrown with other ore minerals. It is characterized by a steel-gray color and metallic luster. Its unique chemical composition, including nickel, bismuth, antimony, arsenic, and sulfur, makes it a subject of scientific interest. ## Physical properties This mineral exhibits a metallic luster and is opaque. Its Mohs hardness is approximately 3. The density has not been precisely measured, but calculated based on its composition and crystal structure, it is 7.19 g/cm³. It shows no cleavage, and its fracture is uneven. ## History and name Jinxiuite was officially recognized by the International Mineralogical Association (IMA) in 2023 (IMA2023-039). The name comes from its discovery locality – the Jinchuan nickel-copper deposit in Gansu Province, China, whose name in Chinese is Jīnchuān (金川).

Properties

Mohs hardness: 3
Luster: Metallic
Streak: Black
Density: 7.19
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Tetragonal

Diagnostic features

## Identification Identification of jinxiuite is impossible without advanced laboratory techniques. It requires analysis by electron microprobe (EDS/WDS) to determine its chemical composition and X-ray diffraction (XRD) to confirm its crystal structure. In polished sections under a reflected light microscope, it has a steel-gray color. ## Distinguishing from similar minerals It can be confused with many other metallic sulfides and sulfosalts, such as pentlandite, gersdorffite, or ullmannite, with which it often co-occurs. Differentiation relies solely on precise chemical analysis. ## Crystal forms Jinxiuite forms exclusively anhedral, irregular grains, often with rounded or embayed boundaries. No well-formed crystals have been observed.

Geological environment

## Genesis Jinxiuite forms as a result of hydrothermal processes in ultramafic igneous rocks. It crystallizes in the late stages of nickel and copper sulfide deposit formation, likely at temperatures below 400°C, in an environment rich in nickel, bismuth, antimony, and arsenic. ## Mineral associations This mineral occurs in close association with pentlandite, maucherite, ullmannite, gersdorffite, cassiterite, chalcopyrite, cubanite, sphalerite, galena, and also with platinum group minerals (PGM). ## Localities The only confirmed occurrence of jinxiuite worldwide is its type locality – the Jinchuan Ni-Cu sulfide deposit, near Jinchang City, in Gansu Province, China.

Rarity

Extremely rare

For collectors

## Quality criteria As a microscopic mineral, jinxiuite is not evaluated based on typical collector criteria such as size or crystal form. Its value is purely scientific and depends on the quality of the analysis confirming its presence and the richness of the mineral association on a given rock fragment. The most valuable specimens are those where jinxiuite grains are relatively large (above 100 micrometers) and clearly visible among other rare minerals.

Care and storage

## Cleaning Due to its extreme rarity and occurrence as microscopic grains intergrown with other minerals, jinxiuite specimens are not subject to standard cleaning. Any attempts at mechanical or chemical cleaning may destroy or remove the mineral. ## What to avoid Avoid contact with chemicals, acids, and ultrasound. Changes in temperature and humidity can affect the host rock and associated minerals. ## Storage Specimens containing jinxiuite should be stored under stable conditions, in specialized "micromount" boxes, protected from dust, moisture, and mechanical damage. It is best to store them in darkness to prevent potential chemical reactions of associated minerals.