Bastnasite
Rare-earth fluorocarbonate ((Ce,La)CO3F)
A rare-earth fluorocarbonate that is one of the world's most important ores of cerium, lanthanum, and other rare earth elements.
- Mohs hardness
- 4-5
- Color
- Yellow, brown, reddish-brown, honey
- Type
- mineral
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Overview
Bastnasite (also spelled bastnaesite or bastnäsite) is a rare-earth fluorocarbonate, (Ce,La)CO3F, and one of the principal ore minerals of the light rare earth elements. It crystallizes in the hexagonal system, typically as yellow to brown waxy or greasy tabular crystals and granular masses.
Named after the Bastnäs mines in Sweden, it is economically critical because it concentrates cerium, lanthanum, neodymium, and related elements used throughout modern technology.
Along with monazite, bastnasite supplies most of the world's rare earth production, with the giant Bayan Obo deposit in China and Mountain Pass in California being the dominant sources.
Formation & geology
Bastnasite forms chiefly in carbonatites and alkaline igneous rocks, where rare-earth-enriched magmas and associated hydrothermal fluids concentrate light rare earth elements.
It also occurs in some hydrothermal veins and in metamorphic and weathered residual deposits derived from such rocks.
The world's most important deposits are the Bayan Obo carbonatite-hosted deposit in Inner Mongolia, China, and the Mountain Pass carbonatite in California, both of which are mined on a large scale for rare earths. Other occurrences include Sweden, Madagascar, and Pakistan, which produces fine collector crystals.
How to identify it
Bastnasite is identified by its yellow, honey-brown, to reddish-brown color, waxy to vitreous or greasy luster, and tabular hexagonal crystals or granular masses. It has a hardness of 4 to 5 and a white to pale streak.
Its color and form resemble several other rare-earth and carbonate minerals, so reliable identification often requires knowing the geologic context (carbonatite or alkaline rock) or instrumental analysis.
Unlike monazite, bastnasite reacts with warm acid because of its carbonate content. Many specimens are weakly radioactive due to thorium impurities, a possible clue.
Uses & significance
Bastnasite is one of the most important ores of the light rare earth elements, supplying cerium, lanthanum, neodymium, and praseodymium. These elements are essential for powerful permanent magnets, catalysts, polishing powders, rechargeable batteries, phosphors, and many electronic and clean-energy technologies.
The strategic importance of rare earths makes bastnasite deposits like Bayan Obo and Mountain Pass globally significant.
For collectors, well-formed honey-colored crystals, especially from Pakistan, are desirable. Because it can contain minor thorium and be slightly radioactive, specimens are best handled and stored sensibly.
Frequently asked questions
What is bastnasite used for?
It is a primary ore of light rare earth elements like cerium and lanthanum, used in magnets, catalysts, polishing powders, and electronics.
Where is bastnasite mined?
The largest sources are the Bayan Obo deposit in China and the Mountain Pass mine in California, both carbonatite-hosted.
Is bastnasite radioactive?
It is often weakly radioactive because it can contain minor thorium, so reasonable handling and storage precautions are sensible.
How is bastnasite different from monazite?
Both are major rare earth ores, but bastnasite is a fluorocarbonate that reacts with acid, while monazite is a phosphate; they often occur together.
Bastnasite guides
In-depth guides for identifying, valuing, and understanding Bastnasite.
