Chenxianite

Chemical formula: AlMn<sub>11</sub>O<sub>16</sub>(OH)<sub>9</sub>

Chenxianite is a very rare aluminum and manganese oxide, forming microscopic, hexagonal crystals with a metallic luster.

## Characteristics Chenxianite is an extremely rare mineral from the oxide group, chemically classified as a hydrated aluminum and manganese oxide. It occurs as very fine, hexagonal, platy crystals, rarely exceeding 20 micrometers in size and 5 micrometers in thickness. It typically forms aggregates with other manganese minerals. Its color is black, and due to the microscopic size of the crystals, its visual characteristics are difficult to observe without specialized equipment. ## Physical Properties Chenxianite crystals exhibit a metallic luster and are opaque. Hardness and density have not been precisely measured due to the small size and rarity of the material. The calculated density is approximately 4.05 g/cm³. ## Colors and Varieties This mineral is uniform in color – it occurs exclusively in black. No varieties have been distinguished. ## History and Name Chenxianite was officially recognized by the International Mineralogical Association (IMA) in 2023 (IMA2023-032). Its name honors Chen Xian (born 1935), a Chinese mineralogist and geochemist, for his contributions to the study of minerals and geological deposits in China. The discovery was made on material from the Wafangzi mine in Liaoning Province, China.

Properties

Luster
Metallic
Streak
Black
Density
4.05
Cleavage
Perfect on {0001}
Transparency
Opaque
Crystal system
Hexagonal

Diagnostic features

## Identification Identification of chenxianite is only possible using advanced analytical methods, such as scanning electron microscopy (SEM) with EDS analysis or X-ray diffraction (XRD). Under collecting or field conditions, identification is impossible due to the microscopic size of the black, hexagonal crystals. ## Distinguishing from Similar Minerals Chenxianite is visually indistinguishable from many other black manganese minerals, such as pyrolusite, cryptomelane, or hollandite, with which it often co-occurs. Certain differentiation requires chemical and structural analysis. ## Crystal Forms It forms very small, hexagonal, platy crystals. They usually occur as dispersed clusters or aggregates on the surface of other minerals.

Geological environment

## Genesis Chenxianite forms as a result of hydrothermal processes in manganese ore deposits. In its type locality (Wafangzi mine), it is a product of alterations of earlier manganese minerals under low-temperature conditions. ## Mineral Associations This mineral co-occurs with other manganese oxides and hydroxides, such as nsutite, pyrolusite, todorokite, cryptomelane, as well as with quartz and calcite. ## Localities The only confirmed locality of chenxianite in the world is its type locality: Wafangzi manganese ore mine, Chaoyang County, Liaoning Province, northeastern China.

Rarity

Extremely rare

For collectors

## Quality Criteria As a micromineral, the collector's value of a specimen depends on the abundance of crystals on the rock matrix and their association with other rare minerals. Well-formed, albeit microscopic, hexagonal crystals are most desirable. Identification must be analytically confirmed, which significantly increases the specimen's value. ## Popular Localities The only source of chenxianite specimens is the Wafangzi mine in China.

Care and storage

## Cleaning Due to the extremely small size of the crystals and their occurrence as growths on a rock matrix, mechanical cleaning is neither recommended nor possible without risk of damage. Specimens should be protected from dust. ## What to Avoid Contact with chemicals, acids, and ultrasound should be avoided, as these could damage both the mineral itself and co-occurring minerals. It should not be heated or exposed to moisture. ## Storage Chenxianite specimens, as microminerals, should be stored in specialized micromount boxes to protect them from dust, shocks, and mechanical damage. Store under stable room conditions.

Sources

Read more