Chenzhangruite

Chemical formula: Mn₂+Fe₂+Te₄+₄O₁₀

Chenzhangruite is an extremely rare manganese iron tellurite oxide, forming microscopic, black crystals with a metallic luster.

## Characteristics Chenzhangruite is an oxide mineral, chemically a manganese iron tellurite. It occurs as extremely small, tabular or bladed crystals, reaching sizes up to 100 micrometers. It typically forms aggregates or appears as single, isolated crystals. It is opaque, black in color, and has a black streak. ## Physical Properties This mineral is characterized by a metallic luster. Its Mohs hardness has not been precisely determined but is estimated to be around 3. The density calculated from the chemical formula and unit cell parameters is 5.83 g/cm³. It exhibits perfect cleavage in one direction. ## History and Name Chenzhangruite was discovered in the Dongping gold mine, Zhangjiakou Prefecture, Hebei Province, China. It was approved as a new mineral species by the International Mineralogical Association (IMA) in 2023 (IMA2023-089). Its name honors Professor Zhangru Chen (b. 1937), a Chinese geologist and mineralogist from Peking University, for his contributions to the study of tellurium-type gold deposits.

Properties

Mohs hardness: ~3
Luster: Metallic
Streak: Black
Density: 5.83
Cleavage: Perfect on {010}
Fracture: Uneven
Transparency: Opaque
Crystal system: Orthorhombic

Diagnostic features

## Identification Identification of chenzhangruite is possible only through advanced laboratory methods, such as Raman spectroscopy and chemical analysis using an electron microprobe (EDS). Visually, it is a black, metallic mineral forming very small, tabular crystals. ## Differentiation from Similar Minerals It can be confused with other rare, black tellurites or oxides found in the same environment. Definitive differentiation from minerals such as marcasite, pyrite, or other sulfides and oxides requires specialized instrumental analysis. ## Crystal Forms Crystals are tabular or bladed, flattened parallel to {010}. They occur as single crystals or in small clusters.

Geological environment

## Genesis Chenzhangruite forms as a result of hydrothermal processes in quartz-calcite veins associated with gold and tellurium deposits. In its type locality (Dongping mine), it is a product of crystallization from moderate-temperature hydrothermal solutions. ## Mineral Associations This mineral is associated with quartz, calcite, native gold, pyrite, marcasite, galena, and other tellurides and tellurites. ## Localities The only confirmed occurrence of chenzhangruite worldwide is its type locality – the Dongping gold mine, Hebei, China.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, the collector's value of chenzhangruite is primarily determined by its extreme rarity and scientific status. Specimens with well-formed crystals, despite their small size, and whose identity has been analytically confirmed, are most highly prized. A rich association with other minerals, especially native gold, is also significant.

Care and storage

## Cleaning Due to the extremely small size of the crystals and their rarity, mechanical cleaning is not recommended and is usually unnecessary. Specimens should be protected from dust in specialized boxes. ## What to Avoid Avoid contact with chemicals, especially acids, which can damage the mineral. Ultrasonic cleaning and steam cleaning should also be avoided. Due to its perfect cleavage, the mineral is susceptible to mechanical damage. ## Storage Chenzhangruite specimens, as microminerals, should be stored under stable conditions in dedicated "micromount" boxes, which protect them from physical damage, dust, and sudden changes in humidity.

Sources

IMA Mineral List (CNMNC)