Peisleyite is a rare phosphate mineral typically found as white, fibrous or chalky crusts and aggregates in phosphate-rich outcrops. It is predominantly identified from its type locality at Tom's Quarry in South Australia, where it forms in association with other rare phosphate species. Collectors generally encounter it as small, unassuming specimens that require magnification to appreciate the fine fibrous structure.
Is this peisleyite?
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 peisleyite with a known reference. Peisleyite sits at Mohs ~3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: earthy.
- 4Match the color rangeCompare against the expected color range: white.
- 5Look at form & habitCrystal system: triclinic. Typical habit: compact.
Often confused with
Peisleyite 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. ~3); luster reads earthy on Peisleyite and vitreous on Wardite.
How to tell apart: Millisite is the harder of the two (Mohs 5.5 vs. ~3); luster reads earthy on Peisleyite and vitreous on Millisite.
All properties
- Chemical formula
- Na₃Al₁₆(PO₄)₁₀(SO₄)₂(OH)₁₇·20H₂O
- Mohs hardness
- ~3
- Density
- 2.20 g/cm³
- Colors
- Streak
- White
- Luster
- Earthy
- Transparency
- Semitransparent
- Crystal system
- Triclinic
- Crystal habit
- Compact
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare secondary mineral in phosphate beds in limestone
Where rockhounds find peisleyite
Classic worldwide localities
- Tom’s Phosphate quarry, near Kapunda, Mount Lofty Ranges, South Australia
Field-hunting tip
Where it forms: A rare secondary mineral in phosphate beds in limestone. If you start seeing f-rich wavellite in float, you are in the right ground. Typical habit: compact. Train your eye for that shape before scanning the outcrop.
Common questions
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Find peisleyite on the map
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