Bastnäsite is a rare-earth fluorocarbonate and, with monazite, one of the two largest sources of cerium and other rare-earth elements. The IMA recognizes four bastnäsite minerals, named for the dominant rare-earth element (Ce, La, Nd and Y), and most bastnäsite is the cerium member; the physical properties here are for bastnäsite-(Ce). It is named for the Bastnäs mine in Sweden, where it was described in 1838. It occurs in alkali granites, syenites, pegmatites and carbonatites, is the leading ore mineral at Mountain Pass, California, and forms very high-quality specimens in the Zagi Mountains of Pakistan.
Is this bastnäsite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch bastnäsite with a known reference. Bastnäsite sits at Mohs 4-5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to greasy.
- 4Match the color rangeCompare against the expected color range: yellow, reddish brown.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: massive, prismatic.
Often confused with
Bastnäsite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside bastnäsite
Minerals reported to co-occur with bastnäsite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ce,La)CO₃F
- Mohs hardness
- 4-5
- Density
- 4.95-5 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous to greasy
- Transparency
- Transparent
- Crystal system
- Hexagonal
- Crystal habit
- Massive, prismatic
- Cleavage
- Imperfect on {1011}; indistinct on {0001}
- Uses
- Ore of rare earth elements
- Host rock
- Alkali granite, syenite and associated pegmatites; carbonatites and associated fenites
Where rockhounds find bastnäsite
Classic worldwide localities
- Bastnäs mine, Riddarhyttan, Sweden (type locality)
- Mountain Pass, California, USA
- Bayan Obo, Inner Mongolia, China
- Zagi Mountains, Pakistan
- Fen Complex, Norway
Field-hunting tip
Where it forms: Alkali granite, syenite and associated pegmatites; carbonatites and associated fenites. If you start seeing monazite, barite, calcite in float, you are in the right ground. Typical habit: massive, prismatic. Train your eye for that shape before scanning the outcrop.
More bastnäsite photos
Common questions
How do you identify bastnäsite?+
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What rocks look like bastnäsite?+
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Find bastnäsite on the map
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