Mckelveyite-(Nd)

Chemical formula: NaCaBa<sub>3</sub>Nd(CO<sub>3</sub>)<sub>6</sub>·3H<sub>2</sub>O

A rare sodium, calcium, barium, and neodymium carbonate, forming small, hexagonal crystals with a vitreous luster.

## Characteristics Mckelveyite-(Nd) is a hydrated carbonate belonging to the mckelveyite group. It occurs as small, tabular or prismatic crystals with a hexagonal outline, rarely exceeding 1 mm in size. Crystals often form rosette-like or spherulitic aggregates. It is a transparent to translucent mineral with a vitreous luster. ## Physical Properties The mineral is characterized by a hardness in the range of 3.5-4 on the Mohs scale and a density of approximately 3.61 g/cm³. It exhibits distinct cleavage in one direction. ## Colors and Varieties Typical colors of mckelveyite-(Nd) are pale green, yellowish-green to almost colorless. No commercial or colored varieties are distinguished. ## History and Name The mineral's name refers to its dominant rare earth element - neodymium (Nd) - and its relationship to mckelveyite-(Y), which is yttrium-dominant. It was approved as a new mineral species by the International Mineralogical Association (IMA) in 2003. It was described based on material from its type locality in Russia. ## Uses Due to its rarity and small crystal size, mckelveyite-(Nd) has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals and for scientists.

Properties

Mohs hardness
3.5-4
Luster
Vitreous
Streak
White
Density
3.61
Cleavage
Good on {0001}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Trigonal

Diagnostic features

## Identification Identification of mckelveyite-(Nd) is based on its characteristic crystal form - small, hexagonal tablets, often in rosette form. Its color (usually greenish), vitreous luster, and occurrence environment are also helpful. It reacts vigorously with hydrochloric acid, which is a diagnostic feature for carbonates. However, definitive confirmation requires advanced chemical analyses (EDS/WDS) to determine its composition, especially the dominance of neodymium. ## Distinguishing from Similar Minerals It can be confused with other minerals from the mckelveyite group, such as mckelveyite-(Y). Differentiation is possible only through chemical analysis. It may also resemble other rare earth carbonates, such as ewaldite or burbankite, from which it differs in crystal form and exact chemical composition. ## Crystal Forms It forms small, tabular crystals with a hexagonal outline. They often occur as radial, rosette-like, or spherulitic aggregates, growing on other minerals.

Geological environment

## Genesis Mckelveyite-(Nd) is a hydrothermal mineral. It forms in the late stages of crystallization in carbonatite deposits or in pegmatites associated with alkaline rock massifs. It crystallizes from solutions rich in sodium, barium, and rare earth elements. ## Mineral Associations It co-occurs with other rare minerals typical of its formation environment. In the type locality (Kovdor Massif, Russia), it was found in association with burbankite, calcite, cordylite-(Ce), ewaldite, and nenadkevichite. ## Localities This is an extremely rare mineral, known from only a few locations worldwide. The most important and well-documented occurrences are: - Kovdor Massif on the Kola Peninsula in Russia (type locality). - Mont Saint-Hilaire alkaline complex in Quebec, Canada, known for the occurrence of many rare minerals.

Rarity

Extremely rare

For collectors

## Quality Criteria For collectors, the quality and form of crystal development are most important. Specimens with sharp, well-defined, hexagonal crystals forming aesthetic, rosette-like aggregates are most valued. Contrast with the matrix mineral on which they grow is also important. Crystal size is crucial - specimens with crystals exceeding 1 mm are considered exceptional. The intensity of the green color can also enhance the specimen's attractiveness. ## Popular Localities By far the most sought-after specimens by collectors come from two classic localities: the Kovdor Massif in Russia and Mont Saint-Hilaire in Canada. Each of these localities provides specimens with slightly different characteristics, valued by specialists.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its sensitivity to chemicals, the use of any chemical agents or ultrasonic cleaners is not recommended. If liquid is necessary, the specimen can be very carefully rinsed with distilled water and immediately dried. ## What to Avoid Avoid contact with acids, which rapidly decompose the mineral. It is sensitive to high temperatures and sudden temperature changes. Prolonged exposure to strong sunlight is not advisable. ## Storage It is recommended to store specimens in stable conditions, in closed display boxes, to protect them from dust, mechanical damage, and sudden changes in humidity. The mineral's brittleness requires careful handling.

Sources

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