Cordylite-(Ce)

Chemical formula: (Na,Ca,◻)BaCe³⁺₂(CO₃)₄(F,O)

Cordylite-(Ce) is a rare mineral from the carbonate group, distinguished by its hexagonal crystals with a vitreous luster and characteristic yellowish coloration.

## Characteristics Cordylite-(Ce) is a complex, hydrated barium, cerium, and sodium carbonate, belonging to the cordylite group. It forms characteristic, hexagonal, tabular or short-prismatic crystals, often terminated by flat basal faces. Specimens are typically small, rarely exceeding a few millimeters. Crystal surfaces may exhibit delicate striations. The mineral is transparent, with a vitreous luster, which gives it an attractive appearance. ## Physical Properties Its Mohs hardness is 4.5, making it a relatively soft mineral. The density is quite high at 4.31 g/cm³, which is noticeable even in small specimens. It exhibits cleavage in the basal plane {0001}, and its fracture is conchoidal. ## Colors and Varieties Cordylite-(Ce) is most often colorless to pale yellow or yellowish. In transmitted light, its color is described as colorless to pale yellow. There are no named color varieties or commercial varieties. ## History and Name The mineral was first described in 1897 by Gustaf Flink. Its name comes from the Greek word "κορδύλη" (kordyle), meaning "club" or "cudgel," in reference to the shape of some of its crystals. The suffix "-(Ce)" indicates the dominance of cerium in the chemical composition, in accordance with the naming rules for rare-earth element minerals. ## Uses Cordylite-(Ce) has no industrial applications. It is solely an object of interest for collectors of rare minerals and scientists studying pegmatites and rare-earth element minerals.

Properties

Mohs hardness
4.5
Luster
Vitreous
Streak
white
Density
4.31
Cleavage
On {0001}. (perhaps a parting)
Fracture
Conchoidal
Transparency
Transparent
Crystal system
Hexagonal

Diagnostic features

## Identification A key diagnostic feature of Cordylite-(Ce) is its hexagonal, tabular crystal habit. Its relatively high density, vitreous luster, and pale yellow color are also characteristic. It reacts violently with hydrochloric acid, which is typical for carbonates. ## Distinguishing from Similar Minerals It can be confused with other rare carbonates from the bastnäsite or synchysite groups, which often co-occur with it and have similar colors. Differentiation requires precise analysis of crystal shape (cordylite is hexagonal, while many similar minerals are trigonal) or advanced analytical methods (XRD, EDS). ## Crystal Forms It crystallizes in the form of hexagonal, tabular or short, prismatic columns. Crystals often occur as single, well-formed individuals embedded in the host rock or in the form of small aggregates.

Geological environment

## Genesis Cordylite-(Ce) is a hydrothermal mineral, primarily associated with nepheline-syenite pegmatites. It forms in the late stages of crystallization of these rocks, in an environment rich in rare-earth elements, barium, and fluorine. ## Mineral Associations It often co-occurs with other minerals typical of agpaitic pegmatites, such as aegirine, nepheline, eudialyte, synchysite-(Ce), bastnäsite-(Ce), neptunite, lorenzenite, and fluorite. ## Localities The most important and classic occurrence (type locality) is the Narssârssuk pegmatite in Greenland, from which the best-known specimens originate. This mineral is also found in the Ilímaussaq alkaline complex (also in Greenland), on the Kola Peninsula in Russia (Khibiny and Lovozero massifs), and in Mont Saint-Hilaire in Quebec, Canada.

Rarity

Rare

For collectors

## Quality Criteria The most valued specimens by collectors are those with well-formed, sharp, undamaged crystals of distinct hexagonal form. Transparent crystals with a more intense, yellow color are rated higher. An important factor is also the contrasting rock matrix on which the crystals are embedded, and the association with other rare minerals. ## Popular Localities By far the most desired specimens come from the type locality - Narssârssuk in Greenland. These are considered the global standard for this mineral. Specimens from Mont Saint-Hilaire in Canada and the Kola Peninsula in Russia are also valued, although they usually achieve smaller sizes.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, distilled water can be used, but prolonged soaking should be avoided. Ultrasonic cleaners, which can damage the crystals, should not be used. ## What to Avoid The mineral is sensitive to acids, which cause it to effervesce violently and decompose. Contact with household and laboratory chemicals should be avoided. Due to its relatively low hardness, it is susceptible to scratches. ## Storage Collector's specimens of Cordylite-(Ce) are best stored in separate, padded boxes to protect them from mechanical damage and contact with harder minerals. They should be protected from dust and sudden temperature changes.

External references

Sources

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