Taranakite is a rare phosphate mineral formed by the reaction of guano-derived phosphoric acid with aluminous rocks, typically found in limestone caves. It usually occurs as fine-grained, chalky-looking masses or thin crusts that exhibit a characteristic pearly luster upon close inspection.
Is this taranakite?
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 taranakite with a known reference. Taranakite 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. Taranakite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Taranakite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: white, yellowish-white, pale yellow.
- 5Look at form & habitCrystal system: trigonal. Typical habit: fine-grained aggregates, crusts, rosettes.
Often confused with
Taranakite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside taranakite
Minerals reported to co-occur with taranakite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₃Al₅(PO₄)₂(HPO₄)₆·18H₂O
- Mohs hardness
- 3.5
- Density
- 2.16-2.17 g/cm³
- Streak
- White
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Fine-grained Aggregates, Crusts, Rosettes
- Cleavage
- Perfect Basal
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Guano Deposits in Limestone Caves
- Typical price
- $20-100 for small specimens
Where rockhounds find taranakite
Classic worldwide localities
- Taranaki, New Zealand
- Isle of Juan Fernandez, Chile
- Senegal
- Australia
- United States
Field-hunting tip
Look in guano deposits in limestone caves country — that is the host setting where taranakite typically forms. If you start seeing apatite, gypsum, brushite in float, you are in the right ground. Field specimens usually show a fine-grained aggregates, crusts, rosettes habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find taranakite on the map
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