RocksdayBastnäsite vs Monazite
The quickest way to tell Bastnäsite from Monazite: Bastnäsite fizzes; Monazite doesn't.
A rare-earth fluorocarbonate and one of the main ores of cerium and its neighbors. It is heavy and fizzes in acid.
Photo: Kouame, CC BY-SA 3.0
A rare-earth phosphate, slightly radioactive from thorium, concentrated in heavy beach sands.
Photo: Robert M. Lavinsky, CC BY-SA 3.0
Quick tests
- Acid (vinegar or dilute HCl): Bastnäsite fizzes; Monazite doesn't.
Key differences
- Monazite does not fizz and is a phosphate.
Side by side
| Property | Bastnäsite | Monazite |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 4–4.5 | 5–5.5 |
| Luster | Vitreous to greasy | Resinous to vitreous |
| Streak | White | White |
| Colors | Yellow, Brown, Red | Brown, Yellow, Red |
| Crystal system | Hexagonal | Monoclinic |
| Specific gravity | 4.9–5.2 | 4.6–5.4 |
| Formula | (Ce,La)(CO₃)F | (Ce,La,Nd,Th)PO₄ |
| Found in | Mountain Pass, California; Bayan Obo, China | Beach sands of Kerala, India; Brazil |
Properties that are the same for both are grayed out.
How to identify bastnäsite
- Yellow, brown or reddish masses or hexagonal crystals.
- Heavy for a non-metallic mineral.
- Fizzes in acid. Hardness about 4–4.5.
Crystal system: Hexagonal
Full Bastnäsite guide →How to identify monazite
- Small yellow-brown grains or wedge crystals.
- Heavy for its color.
- Weakly radioactive.
Crystal system: Monoclinic
Full Monazite guide →More comparisons
Frequently asked questions
What is the difference between bastnäsite and monazite?
Bastnäsite is a mineral with a Mohs hardness of 4–4.5 and a vitreous to greasy luster, usually yellow, brown or red. Monazite is a mineral with a Mohs hardness of 5–5.5 and a resinous to vitreous luster, usually brown, yellow or red.
How can you tell bastnäsite from monazite?
Bastnäsite fizzes; Monazite doesn't. Monazite does not fizz and is a phosphate.
Could you tell them apart from a blurry close-up?
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