Guangyuanite

Chemical formula: Pb<sup>2+</sup><sub>3</sub>Cl<sub>3</sub>(Se<sup>4+</sup>O<sub>3</sub>)(OH)

Guangyuanite is a very rare lead chloride selenite, forming tiny, tabular crystals of white color with a pearly luster.

## Characteristics Guangyuanite is an extremely rare mineral from the selenite group. It occurs as very small, thin, tabular crystals, reaching sizes up to 0.3 x 0.2 x 0.01 mm. These crystals are colorless to white and often form rosette-like or randomly oriented aggregates. Due to their small size, visual features are difficult to observe without specialized equipment, such as a scanning electron microscope (SEM). ## Physical Properties Guangyuanite crystals exhibit a pearly luster on tabular surfaces and a vitreous luster on other faces. They are transparent. Hardness and density have not been precisely measured due to the small amount of available material; however, the density calculated based on the chemical formula and unit cell parameters is 6.45 g/cm³. ## History and Name The mineral was discovered in a selenium deposit in Yutangba, near the city of Guangyuan in Sichuan Province, China. Its name comes from the city near which the discovery site (type locality) is located. It was approved by the International Mineralogical Association (IMA) in 1993 under number IMA1993-024. The first description of the mineral was prepared by Li Xilin, Li Jiaju, and others in 1994.

Properties

Luster
Pearly, Vitreous
Streak
White
Density
6.45
Cleavage
Perfect on {0001}
Transparency
Transparent
Crystal system
Trigonal

Diagnostic features

## Identification Identification of guangyuanite is possible only through advanced analytical methods, such as scanning electron microscopy (SEM) with EDS analysis or X-ray diffraction (XRD). Visual identification in the field or even in a collection is impossible due to the microscopic size of the crystals and similarity to other secondary lead minerals. ## Distinguishing from similar minerals Guangyuanite can be confused with other colorless or white secondary lead minerals, such as cerussite, anglesite, or other selenites and chlorides. Definitive distinction requires specialized chemical analysis confirming the presence of lead, selenium, and chlorine in appropriate proportions. ## Crystal forms Guangyuanite forms very thin, tabular crystals with a hexagonal outline. These crystals often occur as small, rosette-like aggregates or are randomly dispersed on the surface of the host rock.

Geological environment

## Genesis Guangyuanite is a secondary mineral that forms in the oxidation (weathering) zone of carbon-rich selenium deposits. It forms as a result of the reaction of lead- and chlorine-containing solutions with primary selenium minerals. ## Mineral associations At the discovery site, guangyuanite co-occurs with other, often rare, selenium and lead minerals. The most important associated minerals include: clausthalite (lead selenide), tiemannite (mercury selenide), cerussite, anglesite, as well as other selenites such as marthozite and omanuite. ## Localities The only confirmed occurrence of guangyuanite in the world is its type locality – the Yutangba selenium deposit, located in Ziyang County, Guangyuan City Prefecture, Sichuan Province, China.

Rarity

Extremely rare

For collectors

## Quality criteria As a microscopic mineral, guangyuanite is primarily valued by collectors specializing in “micromounts” and rare minerals (so-called “rare species collectors”). The value of a specimen is determined not by its aesthetics, but by the confirmed presence of the mineral itself. Specimens with the largest possible (though still microscopic) and well-formed crystals, as well as rich associations with other rare selenites from this locality, are most highly prized.

Care and storage

## Cleaning Due to the extreme rarity and small size of the crystals, guangyuanite specimens should not be cleaned by any mechanical or chemical means. Any contaminants should be left intact to avoid damaging the delicate crystals. ## What to avoid Avoid contact with any chemicals, including water. Specimens should be protected from vibrations, shocks, dust, and sudden temperature changes. The mineral is sensitive to acids. ## Storage Guangyuanite specimens should be stored exclusively in specialized, sealed “micromount” containers that protect them from mechanical damage and external factors. Store in stable conditions, away from light sources and moisture.

Sources

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