Hongheite

Chemical formula: Ca₁₉Fe₂+Al₄(Fe₃+,Mg,Al)₈(&#₉₇₄₄;,B)₄BSi₁₈O₆₉(O,OH)₉

Hongheite is a very rare mineral from the welinite group, found as tiny, hexagonal crystals in magnesian skarns.

## Characteristics Hongheite is an extremely rare borosilicate mineral belonging to the welinite group. It occurs as very small, hexagonal, tabular or prismatic crystals, reaching up to 0.3 mm in size. It typically forms granular aggregates or appears as single, disseminated crystals in the host rock. It is a black mineral with a metallic luster. ## Physical Properties Hongheite crystals exhibit a hardness of approximately 6 on the Mohs scale. The mineral is brittle, with an uneven fracture. Its calculated density is about 3.75 g/cm³. The luster is metallic, and greasy on fracture surfaces. It is opaque. ## Colors and Varieties Hongheite is a mineral of uniform, black color. No color varieties or commercial varieties are known. ## History and Name The mineral's name comes from the Honghe Hani and Yi Autonomous Prefecture in Yunnan Province, China, where it was discovered. It was first described in 1994 by Chinese mineralogists and approved by the International Mineralogical Association (IMA) under the number IMA1993-019. The type specimen is held by the Geological Museum of China in Beijing. ## Uses Due to its extreme rarity and microscopic crystal sizes, hongheite has no commercial or industrial applications. It is solely an object of scientific interest and a collector's item for specialized rare mineral collectors.

Properties

Mohs hardness: 6
Luster: Metallic
Streak: Black
Density: 3.75
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Hexagonal

Diagnostic features

## Identification Identifying hongheite under amateur conditions is practically impossible. It requires advanced analytical methods such as X-ray diffraction (XRD) and chemical microanalysis (EDS/WDS). It can be preliminarily recognized by its black color, metallic luster, and co-occurrence with characteristic minerals in magnesian skarns from the type locality. ## Distinguishing from Similar Minerals Hongheite can be confused with other black, metallic-lustered minerals found in similar environments, such as magnetite, ilmenite, or spinels. Definitive differentiation is only possible based on chemical and crystallographic analysis. ## Crystal Forms It forms very small, hexagonal crystals with a tabular or short-prismatic habit, usually less than 0.3 mm in size. It occurs as single, disseminated crystals or in granular aggregates.

Geological environment

## Genesis Hongheite forms as a result of contact metamorphism processes. It occurs in magnesian skarns that formed at the contact of a syenite intrusion with dolomites. It is a late-stage mineral in skarn formation. ## Mineral Associations In its type locality (Gejiu, China), hongheite co-occurs with minerals such as: sapphirine, surinamite, strontian spinel, sinoite, fluorite, chondrodite, diopside, calcite, dolomite, titanite, apatite, graphite, and pyrite. ## Localities The only confirmed locality for hongheite in the world is its type locality – the Gejiu tin deposit in Honghe Prefecture, Yunnan Province, southern China.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of hongheite specimens is primarily assessed based on the richness and quantity of crystals on the rock matrix, as well as their degree of development, visible under a microscope. Due to the microscopic nature of the mineral, the aesthetics of the specimen as a whole (matrix) are of secondary importance. The confirmed presence of the mineral is paramount. ## Popular Localities The only source of hongheite specimens is its type locality in Gejiu, China. Specimens from this location are extremely difficult to acquire and appear on the collector's market sporadically.

Care and storage

## Cleaning Due to the microscopic size of the crystals and their embedding in the host rock, mechanical cleaning is neither recommended nor possible without specialized equipment. Specimens should be protected from dust. ## What to Avoid Avoid contact with chemicals, especially strong acids, which can damage the mineral. Also avoid ultrasonic cleaners and sudden temperature changes. Due to its brittleness, specimens are sensitive to impacts and shocks. ## Storage Hongheite specimens are best stored under stable conditions, in sealed "micromount" boxes that protect them from dust, moisture, and mechanical damage. Exposure to strong light is not recommended, although there is no data on its effect on the mineral.

Sources

IMA Mineral List (CNMNC)