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Bastnaesite is a rare gemstone with warm colors ranging from wax yellow to reddish-brown and a vitreous to greasy luster. It is characterized by its high refractive index and weak pleochroism, with gem-quality stones being very uncommon and mostly used for industrial rare-earth element extraction. Its hexagonal crystal system often forms prismatic or tabular crystals, but it is a relatively soft and brittle mineral, making it difficult to cut and generally not suitable for jewelry.

Physical and optical properties

Color: Wax yellow, honey yellow, reddish-brown, or orange-brown.

Luster: Vitreous to greasy or pearly.

Transparency: Transparent to translucent.

Hardness: 4 to 4.5 on the Mohs scale.

Refractive Index: 1.717 to 1.823.

Birefringence: 0.1010.

Dispersion: 0.013.

Pleochroism: Weak.

Crystal System: Hexagonal.

Crystal Habit: Short prisms or tabular rounded crystals.

Composition and origins

Bastnaesite is a rare-earth metal mineral, typically a cerium, lanthanum, and neodymium fluoride carbonate, according to Britannica and The Natural Gem.

It is formed in carbonatites, pegmatites, and contact metamorphic zones.

It is found in many localities worldwide, including China, the United States, Madagascar, Pakistan, and Afghanistan.

Rarity and use

While the mineral itself is not exceedingly rare, high-quality, gem-grade material suitable for faceting is very scarce.

Gem-quality bastnaesite is primarily sought after for its rarity and unique appearance, though its softness makes it challenging to work with.

The mineral's main industrial use is as a source of rare-earth elements.