Yingjiangite

Chemical formula: K₂Ca(U⁶⁺O₂)₇(PO₄)₄(OH)₆·₆H₂O

Yingjiangite is a rare, radioactive uranyl mineral, forming bright yellow, platy crystals and rosette aggregates.

## Characteristics Yingjiangite is a secondary mineral from the uranyl phosphate group, occurring in the oxidation zones of uranium deposits. It forms characteristic, thin, platy crystals with a hexagonal outline, which often combine into rosette or fan-shaped aggregates. Its intense yellow to yellowish-green color is typical for uranyl minerals. ## Physical Properties Yingjiangite crystals are very small, usually not exceeding 1 mm. The mineral exhibits strong, greenish-yellow fluorescence under ultraviolet light (both shortwave and longwave). It is soft and brittle. As a uranium mineral, it is highly radioactive. ## Colors and Varieties This mineral occurs in shades from bright yellow and canary yellow to yellowish-green. No color varieties or commercial varieties are distinguished. ## History and Name The name yingjiangite comes from its discovery locality in 1989 – the Lianshanguan uranium mine in Yingjiang County, Yunnan Province, China. The mineral was described and approved by IMA in 1990. ## Uses Due to its rarity and small crystal size, yingjiangite has no industrial application. It is solely an object of interest for collectors specializing in uranium minerals and for scientific institutions.

Properties

Mohs hardness: 3-4
Color: Yellow, golden-yellow
Luster: Pearly
Streak: Pale yellow
Density: 4.15
Cleavage: Perfect on {100}
Fracture: Uneven
Transparency: Transparent,Translucent
Crystal system: Orthorhombic

Diagnostic features

## Identification Key diagnostic features include its intense yellow color, characteristic rosette aggregates composed of platy crystals, and strong greenish-yellow fluorescence under UV light. Confirmation is provided by radioactivity measurement. ## Distinguishing from Similar Minerals It can be confused with other secondary uranium minerals, such as autunite, meta-autunite, or uranophane. Differentiation often requires chemical analysis (EDS) or X-ray diffraction (XRD). Autunite often forms more square and thicker crystals, while uranophane occurs in acicular or fibrous forms. ## Crystal Forms Yingjiangite crystallizes in very thin, platy crystals with a hexagonal outline. These crystals almost always occur as fan-shaped, spherulitic, or rosette aggregates.

Geological environment

## Genesis Yingjiangite is a secondary mineral, forming in the oxidation (weathering) zones of hydrothermal uranium deposits located in silicate rocks, such as granites. ## Mineral Associations It co-occurs with other uranium minerals, such as uraninite (as a primary mineral), studtite, boltwoodite, kasolite, autunite, metatorbernite, as well as quartz and kaolinite. ## Localities The most important and type locality is the Lianshanguan mine in Yingjiang County, China. This mineral has also been identified in several other locations worldwide, including the Rössing mine in Namibia and the Shinkolobwe mine in the Democratic Republic of Congo.

Rarity

Very rare

For collectors

## Quality Criteria The most prized specimens are those with well-formed, distinct rosette aggregates of intense, pure yellow color, contrasting with the dark matrix rock. The size of the aggregates is a key factor influencing value, as is the absence of damage to the delicate crystals. ## Popular Localities By far the most sought-after specimens by collectors come from the type locality in China (Lianshanguan mine), which has provided the highest quality samples of this mineral.

Care and storage

## Cleaning Yingjiangite specimens should generally not be wet-cleaned. Only gentle dust removal with a soft brush or a stream of compressed air from a safe distance is permissible. ## What to Avoid Contact with water and chemicals should be strictly avoided. The mineral is sensitive to changes in temperature and humidity. As a highly radioactive mineral, it requires special precautions – avoid inhaling dust and direct skin contact. Always wash hands after handling a specimen. ## Storage Specimens should be stored in sealed, lead-lined or thick plastic containers, clearly marked as radioactive material. Store away from other radiation-sensitive minerals, and away from areas of permanent human habitation.