Wakefieldite-(La)

Chemical formula: La<sup>3+</sup>V<sup>5+</sup>O<sub>4</sub>

Wakefieldite-(La) is a rare lanthanum mineral from the vanadate group, forming small, tetragonal crystals with a resinous or adamantine luster.

## Characteristics Wakefieldite-(La) is a lanthanum vanadate belonging to the wakefieldite group. It occurs as very small, usually microscopic, tetragonal crystals. Typical specimens consist of tiny, individual crystals in the form of simple prisms or bipyramids, grown on another mineral. Due to its size, this mineral is mainly of interest to specialized collectors of microscopic specimens (so-called micromounts). ## Physical Properties Its Mohs hardness ranges from 4 to 5. It has a high density of approximately 5.19 g/cm³, which is characteristic of minerals containing rare earth elements. The luster is most often adamantine or resinous. The mineral is translucent, and in thicker fragments, opaque. ## Colors and Varieties Wakefieldite-(La) ranges in color from yellowish, through reddish-brown, to brown. The name with the "-(La)" suffix indicates that lanthanum is the dominant rare earth element in its chemical composition. Other minerals in this group contain predominantly yttrium (wakefieldite-(Y)) or cerium (wakefieldite-(Ce)). ## History and Name The name of the group "wakefieldite" comes from the town of Wakefield in Quebec (Canada), near which wakefieldite-(Y) was discovered. The suffix "-(La)" refers to the dominance of lanthanum. The mineral was first described in 1987 based on findings from the Kasuga mine in Gifu Prefecture, Japan. ## Applications Due to its extreme rarity and occurrence as microscopic crystals, wakefieldite-(La) has no industrial application. It is of scientific and collecting significance only.

Properties

Mohs hardness
4-5
Luster
Adamantine, Resinous
Streak
Pale brown
Density
5.19
Cleavage
Good on {100}
Fracture
Uneven to Subconchoidal
Transparency
Translucent to Opaque
Crystal system
Tetragonal

Diagnostic features

## Identification Identifying wakefieldite-(La) based on visual characteristics is very difficult due to its microscopic size. Key indicators include the tetragonal crystal form (simple bipyramids), high density, adamantine or resinous luster, and the environment of occurrence. Definitive identification requires advanced analytical methods, such as X-ray microanalysis (EDS/WDS) to confirm the presence of lanthanum and vanadium, and X-ray diffraction (XRD) to verify the crystal structure. ## Distinguishing from Similar Minerals Wakefieldite-(La) can be confused with other minerals of similar appearance and habit, such as: - **Xenotime-(Y):** Has an identical crystal structure. Differentiation requires chemical analysis to determine the dominant rare earth element. - **Monazite-(La):** Crystallizes in the monoclinic system, forming crystals of a different shape, often more flattened or wedge-shaped. - **Zircon:** Is significantly harder (7.5 on the Mohs scale). ## Crystal Forms It forms simple, well-developed tetragonal crystals, usually in the form of short prisms terminated by a bipyramid {101}. It occurs as single, grown crystals or small aggregates.

Geological environment

## Genesis Wakefieldite-(La) is a secondary mineral, forming in the late stages of hydrothermal processes. It forms in veins and rock fissures, often as a result of the alteration of earlier rare earth-bearing minerals. ## Mineral Associations It most often co-occurs with other rare earth element minerals. In the type locality (Kasuga mine, Japan), it was found in association with xenotime-(Y), bastnäsite-(La), allanite-(Ce), and shinoite. In other localities, it may occur with monazite, zircon, and various ore minerals. ## Localities This is a very rare mineral, known from only a few locations worldwide. The most important of these are: - **Japan:** Kasuga mine, Ibigawa, Gifu Prefecture - type locality. - **Canada:** Evans-Lou pegmatite, Quebec - source of well-studied specimens. - **Russia:** Khibiny and Kovdor massifs on the Kola Peninsula. - **Italy:** Baveno, Piedmont.

Rarity

Very rare

For collectors

## Quality Criteria The quality of a wakefieldite-(La) specimen is primarily assessed based on the quality of the microcrystals themselves. Specimens with sharp, well-formed, undamaged crystals, even if they are fractions of a millimeter, are most valued. The aesthetics of the matrix and the presence of other rare associated minerals, which enhance the scientific and visual value of the specimen, are also important. ## Popular Localities Specimens from the Kasuga mine in Japan have historical value as those on which the mineral was described. Material from the Evans-Lou pegmatite in Canada is also prized by collectors due to the good quality of the crystals and the thorough scientific investigation of this locality.

Care and storage

## Cleaning Wakefieldite-(La) specimens consist of microscopic crystals that are very delicate and prone to loss. Cleaning should be kept to an absolute minimum. If necessary, a soft brush can be used to remove dust or the specimen can be rinsed with distilled water. Ultrasonic cleaners should be avoided, as they can detach small crystals from the substrate. ## What to Avoid The mineral is sensitive to strong acids. Otherwise, it is relatively stable and does not show sensitivity to light, temperature changes, or humidity under typical collecting conditions. ## Storage It is recommended to store specimens only in specialized micromount boxes, which protect them from dust, mechanical damage, and loss. A label with precise locality information is crucial.

External references

Sources

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