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 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Hannayite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Hannayite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, yellowish-white.
- 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(PO₄)₂·8H₂O
- Mohs hardness
- 2
- Density
- 1.97 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Bladed or Tabular Crystals, Often in Radiating Clusters or Crusts
- Cleavage
- Distinct On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Guano-rich Cave Environments
- Typical price
- $50-300 per specimen
Where rockhounds find hannayite
Classic worldwide localities
- Skipton Caves, Victoria, Australia
- Sand Island, Palmyra Atoll
Field-hunting tip
Look in guano-rich cave environments country — that is the host setting where hannayite typically forms. If you start seeing struvite, newberyite, brushite in float, you are in the right ground. Field specimens usually show a bladed or tabular crystals, often in radiating clusters or crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find hannayite on the map
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