Lepersonnite-(Nd)

Chemical formula: [Nd(H<sub>2</sub>O)<sub>18</sub>(OH)<sub>2</sub>][Nd(U<sup>6+</sup>O<sub>2</sub>)<sub>12</sub>(SiO<sub>3</sub>OH)<sub>2</sub>(CO<sub>3</sub>)<sub>4</sub>(OH)<sub>10</sub>O<sub>2</sub>(H<sub>2</sub>O)<sub>5</sub>]

Lepersonnite-(Nd) is a very rare, radioactive uranyl, neodymium, and silicon mineral, forming characteristic yellow efflorescences and spherulitic aggregates.

## Characteristics Lepersonnite-(Nd) is a complex, hydrated uranyl, neodymium, and silicon carbonate. It occurs as very fine, acicular or fibrous crystals, which most often form radial aggregates, spherulites (spherical clusters), and efflorescences and coatings with a silky or earthy appearance. Its structure is extremely complex, which is typical for secondary uranium minerals. ## Physical Properties This mineral is characterized by a silky luster, and in earthy aggregates, a dull luster. It is translucent. Due to the very small size of its crystals and its fragility, its hardness has not been precisely determined. The density calculated from crystallographic data is approximately 3.97 g/cm³. ## Colors and Varieties Lepersonnite-(Nd) has an intense, canary-yellow color. The name with the -(Nd) suffix indicates that neodymium is the dominant rare earth element in its composition. There is also an analogous mineral with dominant gadolinium, known as lepersonnite-(Gd). ## History and Name The mineral was originally described as lepersonnite-(Gd) in 1981 by Michel Deliens and Paul Piret. It was named in honor of Jacques Lepersonne (1909–1997), a Belgian geologist and director of the geology department at the Royal Museum for Central Africa in Tervuren, for his contributions to the study of African geology. The neodymium-dominant variety, lepersonnite-(Nd), was formally approved as a new mineral in 2021. ## Applications Due to its extreme rarity and status as a micromount mineral, lepersonnite-(Nd) has no industrial applications. However, it is an object of scientific research and a valuable acquisition for specialized collectors of uranium minerals.

Properties

Luster
Silky, Earthy
Streak
Light yellow
Density
3.97
Cleavage
None
Transparency
Translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification The characteristic features of lepersonnite-(Nd) are its canary-yellow color, silky luster, occurrence in the form of radial aggregates and spherulites, and very high radioactivity, easily detectable with a Geiger counter. It occurs as a weathering product of uraninite. ## Differentiation from Similar Minerals It can be confused with many other yellow secondary uranium minerals, such as schoepite, becquerelite, studtite, or uranophane. Definitive differentiation is almost exclusively possible using advanced analytical methods, such as X-ray diffraction (XRD) or energy-dispersive X-ray spectroscopy (EDS), which can confirm the presence of neodymium, silicon, and carbonates in the structure. ## Crystal Forms It forms very fine, acicular or fibrous crystals up to 0.5 mm long. These crystals aggregate into spherical, radial clusters (spherulites) up to 1 mm in diameter, and also form thin efflorescences and coatings on other minerals, mainly on uraninite.

Geological environment

## Genesis It is a secondary mineral, formed in the oxidation (weathering) zone of uranium deposits. It crystallizes as a result of complex hydrothermal and weathering processes, in which waters rich in silica, carbonates, and rare earth elements interact with primary uraninite. ## Mineral Associations It most often co-occurs with other secondary uranium minerals, such as uranophane, schoepite, becquerelite, curite, and bijvoetite-(Y). The primary mineral from which it forms is uraninite. ## Localities The type locality and main source of the best specimens is the Shinkolobwe mine in Katanga Province, Democratic Republic of Congo. This mineral has also been identified in the Krunkelbach uranium deposit in the Black Forest (Germany).

Rarity

Very rare

For collectors

## Quality Criteria Specimen quality for this mineral, which is a typical micromount, is assessed based on the richness and coverage of the matrix, the intensity and purity of the canary-yellow color, and the aesthetics of the aggregates – the better formed and more distinct the spherulites, the more valuable the specimen. Association with other rare uranium minerals adds significant value. ## Popular Localities Specimens from the historic type locality – the Shinkolobwe mine in the DRC – are by far the most valued and sought after by collectors. This locality is known for providing the world's best specimens of many rare uranium minerals.

Care and storage

## Cleaning In principle, cleaning this mineral should be avoided. It is extremely fragile and sensitive. Any attempts at wet cleaning may lead to its damage or dissolution. If necessary, loose dust can be very carefully removed with a soft brush, avoiding the creation of dust. ## What to Avoid **The mineral is highly radioactive.** It is absolutely essential to avoid inhaling dust and ingesting any of its particles. It should be protected from water, chemicals (especially acids), and high temperatures. It should not be stored with minerals that may be damaged by radiation (e.g., smoky quartz, fluorite, topaz). ## Storage Specimens of lepersonnite-(Nd) must be stored in tightly sealed, lead or thick plastic containers, clearly marked with international radioactivity warning symbols. Containers should be kept in an area isolated from living spaces (e.g., in a basement, garage), in a dedicated cabinet, away from places where people spend a lot of time.

Sources

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