Mantienneite is a rare phosphate mineral typically occurring as small, bipyramidal yellow crystals. It is primarily found in complex granite pegmatites and is highly prized by advanced mineral collectors for its scarcity and distinct crystal form.
Is this mantienneite?
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 mantienneite with a known reference. Mantienneite sits at Mohs 2-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Mantienneite leaves a pale brown with a rose tint streak.
- 3Read the lusterHold the specimen under a strong light. Mantienneite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellowish-brown, light brown.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: bipyramidal crystals.
Often confused with
Mantienneite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Wardite is the harder of the two (Mohs 5 vs. 2-3); streak differs, so Mantienneite leaves pale brown with a rose tint, Wardite leaves white.
How to tell apart: Childrenite is the harder of the two (Mohs 5 vs. 2-3); streak differs, so Mantienneite leaves pale brown with a rose tint, Childrenite leaves white; luster reads vitreous on Mantienneite and vitreous to resinous on Childrenite.
Often found alongside mantienneite
Minerals reported to co-occur with mantienneite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K(Mg,Fe³⁺)₂(Al,Fe³⁺)(PO₄)₂(OH,F)₂·8H₂O
- Mohs hardness
- 2-3
- Density
- 2.31 g/cm³
- Streak
- Pale Brown with A Rose Tint
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Bipyramidal Crystals
- Cleavage
- Perfect On {001}; Poor On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Phosphate-rich Granite Pegmatites
Where rockhounds find mantienneite
Classic worldwide localities
- Tip Top mine, Custer, South Dakota, USA
- Panasqueira, Portugal
Field-hunting tip
Look in phosphate-rich granite pegmatites country, the host setting where mantienneite typically forms. If you start seeing quartz, muscovite, triphylite in float, you are in the right ground. Field specimens usually show a bipyramidal crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find mantienneite on the map
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