Alluaudite is a phosphate mineral commonly found as an alteration product of triphylite in complex pegmatites. It typically occurs as yellowish to brownish granular or fibrous masses rather than well-defined crystals, making it a challenging but rewarding find for phosphate mineral enthusiasts.
Is this alluaudite?
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 alluaudite with a known reference. Alluaudite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Alluaudite leaves a yellowish white streak.
- 3Read the lusterHold the specimen under a strong light. Alluaudite typically shows a vitreous to resinous luster.
- 4Match the color rangeCompare against the expected color range: yellow, brown, green, black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous, massive, or granular.
Often confused with
Alluaudite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside alluaudite
Minerals reported to co-occur with alluaudite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Na,Ca)Mn²⁺(Fe³⁺,Mn³⁺,Fe²⁺)₂(PO₄)₃
- Mohs hardness
- 3.5
- Density
- 3.5 g/cm³
- Streak
- Yellowish White
- Luster
- Vitreous to Resinous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous, Massive, Or Granular
- Cleavage
- Distinct On {101}
- Rarity
- Uncommon
- Uses
- Collector, Scientific Research
- Host rock
- Granite Pegmatites
- Typical price
- $20-100 for small cabinet specimens
Where rockhounds find alluaudite
Classic worldwide localities
- France
- Sweden
- USA
- Brazil
- Namibia
Field-hunting tip
Look in granite pegmatites country — that is the host setting where alluaudite typically forms. If you start seeing triphylite, sicklerite, whitlockite in float, you are in the right ground. Field specimens usually show a fibrous, massive, or granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find alluaudite on the map
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