Bastnäsite-(Y)

Chemical formula: YCO<sub>3</sub>F

A rare rare-earth mineral, an yttrium fluorocarbonate, valued by collectors for its well-formed crystals.

## Characteristics Bastnäsite-(Y) is a rare mineral belonging to the bastnäsite group, an yttrium fluorocarbonate. It forms small, tabular or prismatic crystals with a hexagonal outline, often grouped into rosette-like or radial aggregates. It usually occurs as an inclusion within the host rock. Its crystals rarely exceed a few millimeters in size. ## Physical Properties This mineral is characterized by a vitreous or resinous luster. It is relatively soft, with a Mohs hardness of approximately 4 to 4.5. It is a rather brittle mineral with an uneven fracture. The density is significant, around 4.9 g/cm³. ## Colors and Varieties Bastnäsite-(Y) most commonly exhibits colors ranging from yellow, through yellowish-brown, reddish-brown, to brown. Colorless or gray specimens also occur. Its coloration depends on the presence of other trace elements. ## History and Name The name "bastnäsite" comes from the locality of the first discovery of a mineral from this group – the Bastnäs mine in Sweden. The suffix "-(Y)" indicates the dominance of yttrium as the rare-earth element in its chemical composition. The mineral was first described as a distinct species in 1986 by P.J. Dunn and J.A. Nelen. ## Applications Due to its rarity, Bastnäsite-(Y) has no industrial applications. However, it is a mineral of scientific importance, serving as an indicator of specific geochemical conditions, and is a valuable and sought-after object in advanced systematic and regional mineral collections.

Properties

Mohs hardness
4-4.5
Luster
Vitreous to Resinous
Streak
White
Density
4.9
Cleavage
Imperfect on {0001}
Fracture
Uneven
Transparency
Transparent to Translucent
Crystal system
Hexagonal

Diagnostic features

## Identification Field identification of Bastnäsite-(Y) is difficult without specialized equipment. In a collection, it can be preliminarily recognized by its hexagonal crystal shape, relatively high density, and association with other rare-earth minerals. Positive identification requires advanced analytical methods, such as energy-dispersive X-ray spectroscopy (EDS/EDX) to confirm the chemical composition with yttrium dominance. ## Distinguishing from similar minerals It can be confused with other minerals from the bastnäsite group, such as Bastnäsite-(Ce) or Bastnäsite-(La), from which it can only be distinguished by chemical analysis. It may also resemble some micas, but differs from them by the lack of distinct, platy cleavage and significantly higher density. ## Crystal Forms It most often forms thin, tabular crystals with a hexagonal outline. It also occurs as short, prismatic crystals. Crystals often form radial or rosette-like clusters and aggregates.

Geological environment

## Genesis Bastnäsite-(Y) is a mineral of hydrothermal or metamorphic origin. It forms in granitic pegmatites, carbonatites, and altered alkaline rocks rich in rare-earth elements, especially yttrium. ## Mineral Associations It often co-occurs with other rare-earth minerals, such as fluorite, xenotime, allanite, zircon, tengerite-(Y), as well as quartz, microcline, and almandine. ## Localities The most important and well-known occurrences of Bastnäsite-(Y) are found in Norway (pegmatites in the Tysfjord region), Sweden (Östanmossa mine), Russia (Kola Peninsula), and also in the USA (White Cloud Mountains in New Mexico and the Pikes Peak region in Colorado).

Rarity

Rare

For collectors

## Quality Criteria The most prized by collectors are specimens with sharp, well-formed, and clearly visible crystals, especially those forming aesthetic, rosette-like aggregates. The intensity and attractiveness of the color (e.g., vivid yellow or reddish-brown) also increase its value. A contrasting placement on the rock matrix is highly desirable. Crystal size is crucial – specimens with crystals exceeding a few millimeters are exceptionally rare and sought after. ## Popular Localities Specimens from Norwegian pegmatites and the Pikes Peak region in Colorado (USA) are considered classic and among the most desirable on the collector's market.

Care and storage

## Cleaning Utmost caution is recommended. It is best to use compressed air to remove dust. If wet cleaning is necessary, use a soft brush and distilled water, then immediately and thoroughly dry the specimen. Avoid ultrasonic cleaners. ## What to avoid The mineral is sensitive to acids, which can damage or completely dissolve it. Avoid contact with all household and laboratory chemicals. It should not be heated or exposed to sudden temperature changes. ## Storage Specimens should be stored in stable conditions, away from moisture and chemical contaminants. It is best to keep them in sealed display boxes, separated from harder minerals that could scratch them. Due to its brittleness, avoid placing specimens in areas prone to vibrations or falls.

External references

Sources

Read more