Clinofergusonite-(Nd)

Chemical formula: NdNb⁵⁺O₄

Clinofergusonite-(Nd) is a rare niobium and neodymium mineral, forming microscopic, resinous, brown crystals.

## Characteristics Clinofergusonite-(Nd) is a mineral from the fergusonite group, belonging to the oxides. Its composition is dominated by niobium and neodymium. It forms very small, individual crystals not exceeding 0.1 mm in size. They are usually tabular or prismatic. Due to their microscopic size, their visual features are difficult to observe without specialized equipment. ## Physical Properties Crystals exhibit a resinous luster. Hardness and density have not been precisely measured due to the small size of the samples, however, the density calculated based on the formula and unit cell parameters is 6.03 g/cm³. The mineral is brittle. ## Colors and Varieties Observed crystals are brown to reddish-brown. No varieties of this mineral are distinguished. ## History and Name The name "clinofergusonite" refers to its monoclinic symmetry and its relation to the tetragonal mineral fergusonite. The suffix -(Nd) indicates the dominance of neodymium (Nd) as a rare earth element in its structure. The mineral was described by T. V. Subbotina and co-workers in 1987 based on material from the Kola Peninsula in Russia. ## Applications Clinofergusonite-(Nd) has no industrial application. It is of interest only for scientific and collecting purposes for specialists collecting rare earth minerals or so-called "microminerals."

Properties

Mohs hardness: 5.5-6.5
Color: Red, brownish red, yellowish brown
Luster: Resinous
Streak: Pale brown
Density: 6.45
Cleavage: None
Fracture: Sub-Conchoidal
Transparency: Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of clinofergusonite-(Nd) is impossible without advanced analytical techniques, such as energy-dispersive spectroscopy (EDS/EDX) to confirm chemical composition (presence of niobium and neodymium) and X-ray diffraction (XRD) to determine crystal structure. Visually, in the field or in a collection, it is unrecognizable. ## Distinguishing from Similar Minerals It can be confused with other minerals from the fergusonite group, such as fergusonite-(Y), fergusonite-(Ce), or clinofergusonite-(Y). Differentiation requires chemical analysis to determine the dominant rare earth element. Other niobium and tantalum oxides, such as pyrochlore, microlite, or columbite, may also have a similar appearance. ## Crystal Forms It forms small, individual crystals with a tabular or short-prismatic habit, reaching sizes up to 0.1 mm.

Geological environment

## Genesis Clinofergusonite-(Nd) forms in the late stages of crystallization of alkaline pegmatites, rich in rare earth elements and niobium. It is a hydrothermal mineral, crystallizing in altered parts of these rocks. ## Mineral Associations At the type locality (Mount Alluaiw, Lovozero massif), it coexists with microcline, nepheline, aegirine, eudialyte, lorenzenite, lomonosovite, murmanite, natrosilite, and natroniobite. ## Localities The only confirmed and well-described locality of this mineral in the world is Mount Alluaiw in the Lovozero massif on the Kola Peninsula in Russia.

Rarity

Very rare

For collectors

## Quality Criteria Due to its microscopic size, the only criterion for evaluation is the quality and richness of the host specimen. Most desirable are samples with numerous, well-formed microcrystals, preferably in association with other rare minerals. Identification must be analytically confirmed. ## Popular Localities The only source of specimens is the Lovozero massif in Russia. Material from this locality is the standard for this mineral.

Care and storage

## Cleaning Specimens of this mineral are extremely small and brittle, usually embedded in another mineral (matrix). No mechanical or chemical cleaning is recommended, as it could destroy or remove the microscopic crystals. ## What to Avoid Avoid contact with any chemicals, ultrasonics, and sudden temperature changes. The crystals are very brittle and susceptible to mechanical damage. ## Storage Specimens should be stored exclusively in specialized micromount boxes to protect them from dust and physical damage. They do not require special lighting or humidity conditions.

External references

https://www.mindat.org/min-1466.html