Zhengminghuaite

Chemical formula: Cu₁+₆Fe₂+₃As₃+₄S₂-₁₂

Zhengminghuaite is an extremely rare copper, iron, and arsenic sulfide with a metallic luster, occurring as microscopic grains.

## Characteristics Zhengminghuaite is a sulfide mineral belonging to the tetrahedrite group. It occurs as anhedral (irregular) or subhedral (poorly formed) grains not exceeding 100 micrometers in size. Its color ranges from steel-gray to iron-black, with a distinct metallic luster. It is an opaque mineral. ## Physical Properties The Mohs hardness of zhengminghuaite is approximately 4. The density calculated based on the chemical formula and unit cell parameters is 4.59 g/cm³. The mineral is characterized by a metallic luster and a black streak. ## Colors and Varieties This mineral is uniform in color, ranging from steel-gray to black. No varieties are known. ## History and Name Zhengminghuaite was officially recognized by the International Mineralogical Association (IMA) in 2021. Its name honors Chinese mineralogist Zheng Minghua (born 1937), in recognition of his contributions to uranium deposit research in China. The type locality (locus typicus) is the Xiangquan uranium deposit in Guangdong Province, China. ## Applications As an extremely rare mineral occurring only as microscopic grains, zhengminghuaite has no industrial applications. It is solely an object of scientific research and a valuable acquisition for specialized collectors of rare minerals (so-called microminerals).

Properties

Mohs hardness: 4
Luster: Metallic
Streak: Black
Density: 4.59
Transparency: Opaque
Crystal system: Cubic

Diagnostic features

## Identification Amateur identification of zhengminghuaite is impossible due to its microscopic size and appearance typical of many sulfides. Recognition is based on its steel-gray color, metallic luster, and co-occurrence with other minerals in a specific geological environment. Definitive identification requires advanced analytical techniques, such as electron microprobe chemical analysis (EDS/WDS) and X-ray diffraction (XRD). ## Differentiation from Similar Minerals Zhengminghuaite can be easily confused with other gray, metallic sulfides and sulfosalts, such as tetrahedrite, tennantite, arsenopyrite, or galena. Differentiation is possible only through precise chemical analysis, which will reveal the unique proportion of copper, iron, arsenic, and sulfur. ## Crystal Forms The mineral crystallizes in the isometric system, but well-formed crystals are not observed. It occurs as irregular, aggregated grains within the rock mass.

Geological environment

## Genesis Zhengminghuaite forms as a result of hydrothermal processes within stratabound uranium deposits. Its formation is associated with U-V-As-Cu mineralization in sedimentary rocks, such as black shales and siliceous rocks, which have been subjected to hydrothermal solutions. ## Mineral Associations This mineral occurs in association with other ore minerals. In the type locality, its co-occurrence with uraninite, coffinite, brannerite, arsenopyrite, pyrite, galena, sphalerite, tennantite, and native arsenic has been observed. ## Localities The only confirmed occurrence of zhengminghuaite in the world is its type locality – the Xiangquan uranium deposit, in Longchuan County, Heyuan Prefecture, Guangdong Province, China.

Rarity

Extremely rare

For collectors

## Quality Criteria For such a rare micromineral as zhengminghuaite, the main criterion of value is the confirmed presence of the mineral on the specimen itself. An additional advantage is the richness of the mineral association, i.e., the presence of other well-identified associated minerals. The size of the grains, although always microscopic, is also important – the larger and more numerous, the more valuable the specimen. Aesthetics are secondary to scientific and documentary value. ## Popular Localities Specimens come exclusively from one location in the world – the Xiangquan deposit in China, making them extremely difficult to acquire.

Care and storage

## Cleaning Specimens of zhengminghuaite should only be dry-cleaned, using a soft brush to remove dust. Due to its reactivity and the presence of arsenic, contact with water and any chemical agents should be avoided. ## What to Avoid The mineral is sensitive to moisture and atmospheric oxygen, which can cause its slow decomposition (oxidation). Contact with acids, detergents, and other chemicals should be avoided. It is relatively soft, so it must be protected from scratching. ## Storage It is recommended to store specimens in tightly sealed, dry containers (e.g., "perky box" type) to limit air and moisture access. They should be kept away from heat sources and direct sunlight.

Sources

IMA Mineral List (CNMNC)