Lacroixite is a scarce phosphate mineral primarily found in complex granitic pegmatites. It is most easily identified by its distinctive yellow to greenish hues and association with other phosphate minerals, though it is often mistaken for amblygonite without chemical analysis.
Is this lacroixite?
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 lacroixite with a known reference. Lacroixite sits at Mohs 4.5-5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Lacroixite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Lacroixite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellow-green, colorless, pink.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: rarely as small prismatic crystals, commonly massive or granular.
Often confused with
Lacroixite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside lacroixite
Minerals reported to co-occur with lacroixite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaAlFPO₄
- Mohs hardness
- 4.5-5
- Density
- 3.32 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Rarely as Small Prismatic Crystals, Commonly Massive or Granular
- Cleavage
- Distinct On {110}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites
- Typical price
- $50-500 depending on specimen quality
Where rockhounds find lacroixite
Classic worldwide localities
- Kreuzberg, Bavaria, Germany
- Aricheng, Piauí, Brazil
- Tsaobismund, Namibia
Field-hunting tip
Look in granite pegmatites country — that is the host setting where lacroixite typically forms. If you start seeing amblygonite, fluorapatite, quartz in float, you are in the right ground. Field specimens usually show a rarely as small prismatic crystals, commonly massive or granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find lacroixite on the map
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