Hannayite is a rare phosphate mineral typically formed through the reaction of bat guano with magnesium-rich sediments in cave environments. It is most famous for its occurrence in the Skipton Caves of Australia, where it appears as delicate, clear-to-white tabular crystals often associated with struvite.
Is this hannayite?
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 hannayite with a known reference. Hannayite 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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: yellow.
- 5Look at form & habitCrystal system: triclinic. Typical habit: bladed or tabular crystals, often in radiating clusters or crusts.
Often confused with
Hannayite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside hannayite
Minerals reported to co-occur with hannayite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (NH₄)₂Mg₃(PO₃OH)₄·8H₂O
- Mohs hardness
- 2-3
- Density
- 2.03 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Triclinic
- Crystal habit
- Bladed or tabular crystals, often in radiating clusters or crusts
- Cleavage
- Good on {001}; poor on {110}, {110}, and {130}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As rare druses on guano-derived phosphate mineral crusts in caves
Where rockhounds find hannayite
Classic worldwide localities
- Skipton lava tube caves, 40 km southwest of Ballarat, Victoria, and in the Murra-el-elevyn Cave, Cocklebiddy, Western Australia
- Niah Great Cave, Sarawak, Malaysia
Field-hunting tip
Where it forms: As rare druses on guano-derived phosphate mineral crusts in caves. If you start seeing biphosphammite, guanine, monetite in float, you are in the right ground. Typical habit: bladed or tabular crystals, often in radiating clusters or crusts. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify hannayite?+
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What rocks look like hannayite?+
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Find hannayite on the map
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