Yunhaoite

Chemical formula: K<sub>2</sub>(Mo<sup>6+</sup>O<sub>4</sub>)

Yunhaoite is a very rare, water-soluble potassium molybdate, forming colorless, tabular crystals with a pearly luster.

## Characteristics Yunhaoite is a naturally occurring potassium molybdate. This mineral forms colorless, transparent, tabular crystals, often hexagonal in outline, reaching up to 0.2 mm in size. It occurs as single crystals or small aggregates. Due to its water solubility, it is an unstable mineral in humid environments. ## Physical Properties Yunhaoite crystals exhibit perfect cleavage in one direction, resulting in a pearly luster on cleavage surfaces, while other faces show a vitreous luster. It is a very soft mineral. ## Colors and Varieties Yunhaoite is colorless. No varieties have been distinguished. ## History and Name The mineral was approved by the IMA in 2023 (IMA2023-030). Its name honors Yunhao Sun (born 1945), a Chinese geologist and expert in molybdenum deposit geology, for his contributions to research on these deposits in China. It was discovered in the Qiaoxia molybdenum mine in Zhejiang Province, China. ## Uses Yunhaoite has no practical applications and is of purely scientific and collector's interest for specialized collectors.

Properties

Mohs hardness
2
Luster
Pearly, Vitreous
Streak
White
Density
3.03
Cleavage
Perfect on {0001}
Fracture
Micaceous
Transparency
Transparent
Crystal system
Trigonal

Diagnostic features

## Identification The key diagnostic feature of yunhaoite is its complete water solubility. Other features include its colorless nature, tabular crystal habit, perfect cleavage, and pearly luster on cleavage planes. ## Distinguishing from similar minerals It can be confused with other colorless, tabular secondary minerals. The water solubility test is the simplest way to distinguish it. It is impossible to distinguish from synthetic potassium molybdate (K₂MoO₄) without advanced studies. ## Crystal forms It forms thin, tabular crystals, often with a hexagonal outline. It occurs as single plates or small, loose aggregates.

Geological environment

## Genesis Yunhaoite is a secondary mineral that formed as a result of post-magmatic processes. It crystallizes directly from hot, molybdenum- and potassium-rich hydrothermal solutions or volcanic gases (fumaroles) within molybdenum deposits. ## Mineral associations At its type locality, it is associated with molybdenite, pyrite, quartz, and fluorite. ## Localities The only known occurrence of this mineral in the world is the Qiaoxia molybdenum mine, Qingtian County, Zhejiang Province, eastern China.

Rarity

Extremely rare

For collectors

## Quality criteria As a microscopic and extremely rare mineral, the main criterion for value is the confirmed presence of the mineral on a fragment of the host rock itself. Well-formed, even small crystals with a distinct outline are most desirable. The size of the specimen is not crucial; the quality of the microcrystals matters. ## Popular localities The only source of specimens is the type locality – the Qiaoxia mine in China.

Care and storage

## Cleaning The mineral must not be cleaned wet. It is completely water-soluble. Any contact with liquids should be avoided. ## What to avoid Contact with water, water vapor, and high air humidity, which can dissolve or damage the specimen, must be strictly avoided. It should be protected from all chemicals and sudden temperature changes. ## Storage Yunhaoite specimens must be stored in airtight, sealed containers, preferably with a desiccant (e.g., silica gel). They should be displayed away from sources of moisture and direct sunlight.

Sources

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