Wumuite
Chemical formula: KAl₀.₃₃W⁶⁺₂.₆₇O₉
Wumuit is a rare tungstate mineral characterized by its hexagonal structure and light green color, discovered in China.
Properties
- Mohs hardness
- 5-6
- Luster
- Vitreous
- Streak
- White
- Density
- 6.52
- Cleavage
- Parallel to <mi>{10_10}</mi> and {0001}.
- Transparency
- Transparent
- Crystal system
- Hexagonal
Diagnostic features
## Identification Amateur identification of wumuit is practically impossible due to its microscopic size and occurrence. Identification requires advanced analytical methods, such as Raman spectroscopy or chemical analysis using an electron microprobe (EDS/WDS). A visual feature that might only suggest its presence is finding light green, hexagonal crystals in association with tungsten minerals in known localities. ## Distinguishing from Similar Minerals Due to its unique chemical composition and structure, it is not easily confused with other minerals after analysis. Visually, without examination, it could be mistaken for other microscopic, green secondary minerals. ## Crystal Forms Wumuit forms hexagonal, tabular or platy crystals. It occurs as single, dispersed crystals or small aggregates on the surface of other minerals.
Geological environment
## Genesis Wumuit is a secondary mineral that forms in the oxidation zones of hydrothermal tungsten deposits. It is created through the weathering and alteration of primary tungsten ores, such as scheelite or wolframite, in the presence of potassium- and aluminum-rich solutions. ## Mineral Associations This mineral co-occurs with other tungsten minerals, both primary and secondary. In its type locality, it was found in association with scheelite, quartz, muscovite, pyrite, and the rare mineral sanmartinite. ## Localities The only confirmed and described occurrence of wumuit in the world is its type locality: the Nanyang tungsten deposit, in Huaping County, Lijiang Prefecture (Yunnan Province, China).
Rarity
Very rare
For collectors
## Quality Criteria The quality of wumuit specimens is primarily assessed based on the presence of well-formed, sharp, and undamaged crystals, even if they are microscopic in size. Higher color contrast with the host rock (matrix) and an abundance of crystals on the specimen's surface increase its collector's value. Due to their size, specimens are evaluated under a microscope. ## Popular Localities The only source of wumuit specimens is its type locality in China. All materials available on the collector's market originate from this single location.
Care and storage
## Cleaning Specimens should be cleaned very carefully, using compressed air to remove dust. Due to the microscopic size of the crystals, contact with water or brushes is not recommended and can lead to their damage or loss. ## What to Avoid Avoid contact with chemicals, acids, and detergents. The mineral should be protected from ultrasound, high temperatures, and sudden temperature changes. It should also be protected from mechanical damage and abrasion. ## Storage It is recommended to store specimens in specialized, sealed "micromount" boxes, which protect them from dust, moisture, and physical damage. Display should be away from direct sunlight and heat sources.