Mianningite

Chemical formula: (Fe²⁺,U,Pb)₂(Ti,Fe³⁺)O₁₂(?)

Mianningite is a rare, black oxide mineral of the crichtonite group, containing titanium, iron, and uranium.

## Characteristics Mianningite is a very rare oxide mineral belonging to the crichtonite group. It forms small, tabular or short-prismatic crystals with a hexagonal outline, reaching sizes up to 1 mm. It occurs as inclusions in other minerals. It is opaque and black in color. ## Physical Properties This mineral is characterized by a hardness of 6 on the Mohs scale and a density of 4.62 g/cm³. It has a black streak and a metallic luster. The fracture is conchoidal. Due to its uranium content, it is radioactive. ## History and Name The mineral's name comes from its discovery locality – Mianning County in Sichuan Province, China. It was approved as a new mineral by the International Mineralogical Association (IMA) in 1992. ## Applications Due to its extreme rarity, mianningite has no industrial applications. It is solely an object of scientific interest and a collector's item for specialized collectors of rare minerals.

Properties

Mohs hardness
6
Luster
Metallic
Streak
Black
Density
4.62
Fracture
Conchoidal
Transparency
Opaque
Crystal system
Trigonal

Diagnostic features

## Identification Identifying mianningite is extremely difficult without advanced research methods. It can be preliminarily recognized by its black color, metallic luster, and occurrence in a specific geological environment. A key feature, verifiable with a Geiger counter, is its radioactivity. ## Distinguishing from Similar Minerals It can be confused with other black, metallic minerals from the crichtonite group, such as crichtonite, senaite, or lindsleyite. Definitive differentiation is only possible based on chemical composition analysis (EDS/WDS) and X-ray diffraction (XRD) studies. ## Crystal Forms It forms small, hexagonal, tabular crystals, usually less than 1 millimeter in size.

Geological environment

## Genesis Mianningite forms in carbonatite rocks, which are a rare type of igneous carbonate rock. It is a hydrothermal mineral, crystallizing in the late stages of these rocks' formation. ## Mineral Associations At its type locality (Baozi Hill), it co-occurs with aegirine, fluorite, barite, monazite-(Ce), and aeschynite-(Y). ## Localities The only confirmed and described occurrence of mianningite in the world is its type locality: Baozi Hill in Mianning County, Liangshan Yi Autonomous Prefecture, Sichuan Province, China.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a mianningite specimen primarily depends on its presence and identifiability. The most desirable specimens are those with well-formed, even if microscopic, crystals, embedded in a contrasting background of associated minerals. Any analytically confirmed specimen is extremely valuable to specialized collectors. ## Popular Localities The only source of mianningite specimens is its type locality in China. Material from this location is extremely difficult to obtain.

Care and storage

## Cleaning Mianningite specimens are generally not cleaned due to their small size and occurrence as inclusions in the host rock. Any attempts at mechanical or chemical cleaning can irreversibly damage the mineral. ## What to Avoid Avoid contact with chemicals, acids, and ultrasound. The mineral is radioactive, so caution should be exercised, dust inhalation avoided, and hands washed after each contact. ## Storage Specimens should be stored in closed, labeled containers, away from other radiation-sensitive minerals. It is recommended to store them in a place inaccessible to children and pets, with an appropriate radioactivity warning label.

External references

Sources

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