Bastnäsite-(Nd)
Chemical formula: NdCO<sub>3</sub>F
A rare mineral from the bastnäsite group, a neodymium fluorocarbonate, characterized by the dominance of this rare earth element.
Description
## Characteristics Bastnäsite-(Nd) is a mineral belonging to the bastnäsite group, in which the rare earth element neodymium dominates over others. It forms small, tabular or short-prismatic crystals with a hexagonal outline, often with striated faces. It also occurs as granular aggregates or embedded grains. Its color ranges from reddish-brown and pinkish-brown to yellowish-brown. The mineral is usually translucent to opaque, with a vitreous luster, and often resinous or greasy on fracture surfaces. ## Physical Properties The hardness of bastnäsite-(Nd) on the Mohs scale is 4 to 4.5, making it a relatively soft mineral. Its density is significant, approximately 5.19 g/cm³, which is typical for minerals containing rare earth elements. It exhibits good cleavage in one plane, and its fracture is uneven to subconchoidal. ## Colors and Varieties The dominant colors are shades of brown, pink, and red, which is associated with the presence of neodymium. There are no named commercial or color varieties; its name precisely defines it as a member of the bastnäsite group with dominant neodymium. ## History and Name The name of the group "bastnäsite" comes from the Bastnäs mine in Sweden, where a mineral from this group (bastnäsite-(Ce)) was first identified. The neodymium-dominant member, bastnäsite-(Nd), was formally described and approved as a new mineral species relatively recently. Its type locality is the Red Cloud mine in the Gallinas Mountains, New Mexico (USA), where it occurs in fluorite veins. ## Applications Due to its rarity, bastnäsite-(Nd) has no industrial application as an ore of neodymium. However, it is a valuable object for scientific research on the geochemistry of rare earth elements and is a sought-after collector's mineral.
Diagnostic features
## Identification Helpful identification features include: high density, hexagonal crystal outline, resinous luster on fracture, and characteristic occurrence environment (REE-rich veins, carbonatites). Reaction with acid (effervescence) is a diagnostic feature for carbonates, but it destroys the sample. ## Distinguishing from Similar Minerals Distinguishing bastnäsite-(Nd) from other minerals of the bastnäsite group (e.g., the much more common bastnäsite-(Ce)) is impossible without advanced analytical methods, such as X-ray microanalysis (EDS/WDS). It can be confused with monazite, which is, however, harder and crystallizes in a different system. ## Crystal Forms Crystals are typically tabular or short, hexagonal prisms. It often forms granular, rosette-like aggregates or occurs as irregular masses embedded in the host rock.
Geological environment
## Genesis Bastnäsite-(Nd) is a mineral of hydrothermal origin. It forms in the final stages of crystallization from solutions rich in fluorine, carbon dioxide, and rare earth elements. It most commonly forms in ore veins, especially fluorite-barite veins, as well as in carbonatites and alkaline rocks. ## Mineral Associations It often co-occurs with fluorite, barite, celestine, calcite, quartz, and other rare earth minerals such as synchysite, parisite, monazite, or allanite. ## Localities The most important and type locality is the fluorite veins in the Red Cloud mine, Gallinas Mountains, New Mexico, USA. It has also been identified in other locations with elevated REE concentrations, for example, in the Pajarito complex in New Mexico.
Rarity
Very rare
Collector aspects
## Quality Criteria The most highly valued by collectors are specimens with well-formed, sharp crystals of intense, pinkish-brown color. Crystals embedded on a contrasting matrix, such as white barite or purple fluorite, are particularly desirable. The size of the crystals, their transparency, and the absence of damage significantly increase the value of the specimen. ## Popular Localities The vast majority of the best collector specimens come from the type locality – the Red Cloud mine in New Mexico, USA. Specimens from other locations are extremely rare on the market.
Care and storage
## Cleaning Specimens should be cleaned very carefully, using a soft brush and distilled water. Ultrasonic cleaners or strong jets of water, which could damage delicate crystals, are not recommended. ## What to Avoid The mineral is a carbonate and reacts violently with acids, even weak ones, leading to its destruction. Contact with all chemicals should be avoided. It is not sensitive to light, but extreme temperature changes should be avoided. ## Storage It is recommended to store specimens in separate, padded boxes or display cases to protect them from scratching by harder minerals (e.g., quartz). Storage in a humid environment should be avoided.