Monazite-(La) is a rare-earth phosphate mineral often found as small, wedge-shaped brownish crystals in pegmatites. Collectors should look for its characteristic resinous luster and distinct crystal habits, though it is frequently identified through X-ray diffraction due to its similarity to other rare-earth minerals. Always handle with care due to its inherent radioactivity from thorium content.
Is this monazite-(la)?
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 monazite-(la) with a known reference. Monazite-(La) sits at Mohs 5-5.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: grayish white.
- 3Read the lusterHold the specimen under a strong light. Luster: resinous, waxy, vitreous to adamantine.
- 4Match the color rangeCompare against the expected color range: yellowish brown, brown, pink, yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: crystalline, twinning common.
Often confused with
Monazite-(La) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Zircon is the harder of the two (Mohs 7.5 vs. 5-5.5); streak differs, so Monazite-(La) leaves grayish white, Zircon leaves white; luster reads resinous, waxy, vitreous to adamantine on Monazite-(La) and vitreous to adamantine; greasy when metamict on Zircon.
How to tell apart: Streak differs, so Monazite-(La) leaves grayish white, Titanite leaves white; luster reads resinous, waxy, vitreous to adamantine on Monazite-(La) and adamantine to resinous on Titanite.
How to tell apart: Streak differs, so Monazite-(La) leaves grayish white, Xenotime leaves white; luster reads resinous, waxy, vitreous to adamantine on Monazite-(La) and vitreous on Xenotime.
Often found alongside monazite-(la)
Minerals reported to co-occur with monazite-(la). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- LaPO₄
- Mohs hardness
- 5-5.5
- Density
- 5.17-5.27 g/cm³
- Streak
- Grayish white
- Luster
- Resinous, waxy, vitreous to adamantine
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Crystalline, twinning common
- Cleavage
- {100}, distinct; {010}, poor
- Rarity
- Uncommon
- Uses
- Collector, Ore of rare earth elements
- Host rock
- In fissure veins, granite and gneissic metamorphic rocks
Where rockhounds find monazite-(la)
Classic worldwide localities
- Kounrad Massif, northern Balkhash region, Kazakhstan
- Kokšín, near Mítov, Czech Republic
- Poiana Marului, Muntele Mic Mountains, Romania
- Gasteiner Tal, Austria
- Ebisie mine, Wada, Gifu Prefecture, Japan
- Ratnapura, Sri Lanka
Field-hunting tip
Where it forms: In fissure veins, granite and gneissic metamorphic rocks. If you start seeing quartz, feldspar, biotite in float, you are in the right ground. Typical habit: crystalline, twinning common. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify monazite-(la)?+
Where is monazite-(la) found?+
Is monazite-(la) safe to handle?+
What rocks look like monazite-(la)?+
What minerals are found with monazite-(la)?+
What kind of rock does monazite-(la) form in?+
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Find monazite-(la) on the map
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