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, 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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