Bastnäsite-(Ce)

Class: Carbonates (Nitrates)
Group: Bastnäsite

The most abundant rare earth elements-bearing mineral, typically hydrothermal, although primary igneous occurrences are known; in granite and alkali syenites and pegmatites; in carbonatites (Anthony et al., 2001—2005). Faceted specimens are very rare.

Bastnäsite-(Ce) — specimen 0280, photo © NMNHS

Original description: ‘Bastnaesite’ Huot, J. J. N., 1841. Genre. Lanthane. 2 Espèce, Bastnaesite — Manuels-Roret. Nouveau Manuel Complet de Minéralogie, Paris: 296 [view in ‘Library’].

Type locality: Bastnäs mines, Skinnskatteberg, Västmanland, Sweden.

Type material: Naturhistoriska riksmuseet, Stockholm, Sweden, 23:0476 (Anthony et al., 2001—2005).

Etymology: for its type locality in the Bastnäs mines, Sweden, and the content of cerium.

Distribution: Afghanistan: Kunar; Burundi; Canada: Quebec, Mont Saint-Hilaire; China: Inner Mongolia; Madagascar; Pakistan: Zagi Mountain; Sweden: Bastnäs mines; Tanzania; Turkey: near Eskişehir; USA: California, San Bernardino Co.; Zambia (Anthony et al., 2001—2005).

Chemistry

Ce(CO3)F

Essential elements: carbon (C), oxygen (O), fluorine (F), cerium (Ce).

Crystal data

Crystallography: hexagonal — ditrigonal dipyramidal. Crystal habit: commonly in tabular to equant crystals, to 20 cm; granular, massive (Anthony et al., 2001—2005).

Physical properties

Cleavage: on {1010}, indistinct; {0001}, a parting, distinct to perfect (Anthony et al., 2001—2005). Fracture: uneven (Anthony et al., 2001—2005). Tenacity: brittle (Anthony et al., 2001—2005). Hardness: 4—4.5 (Lazzarelli, 2012). Density: 4.78—5.2 g/cm3 (Lazzarelli, 2012). Luminescence: none. Radioactivity: GRapi 60386.61. Other: strongly piezoelectric; cathodoluminescent (Anthony et al., 2001—2005).

Optical properties

Colour: wax-yellow, honey-yellow, reddish brown; in transmitted light, pale yellow to colourless (Anthony et al., 2001—2005). Diaphaneity: transparent to translucent (Anthony et al., 2001—2005). Lustre: vitreous to greasy (Anthony et al., 2001—2005). Refractive index: 1.72—1.82 — anisotropic [uniaxial (+)] (Lazzarelli, 2012). Birefringence: 0.1. Dispersion: no data. Pleochroism: faint (Anthony et al., 2001—2005).

Material from ‘Repository’

1 specimen: 0280 — 0.75 ct, Afghanistan.

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