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, 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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