Mundrabillaite is a rare ammonium calcium phosphate mineral that typically forms as delicate, needle-like white crusts or efflorescences. It is primarily found in environments where bat guano reacts with calcium-rich substrates in caves or, famously, at the site of the Mundrabilla iron meteorite. Collectors prize it as a scientific curiosity due to its unusual association with phosphate-rich organic decay.
Is this mundrabillaite?
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 mundrabillaite with a known reference. Mundrabillaite 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. Mundrabillaite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Mundrabillaite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: crusts, aggregates of acicular crystals.
Often confused with
Mundrabillaite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside mundrabillaite
Minerals reported to co-occur with mundrabillaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (NH₄)₂Ca(HPO₄)₂·H₂O
- Mohs hardness
- 2
- Density
- 1.65 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Crusts, Aggregates of Acicular Crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Phosphate-rich Cave Deposits, Altered Meteorite Impact Sites
- Typical price
- niche/high, typically found only in research or advanced collections
Where rockhounds find mundrabillaite
Classic worldwide localities
- Mundrabilla meteorite site, Western Australia
- various cave environments
Field-hunting tip
Look in phosphate-rich cave deposits, altered meteorite impact sites country, the host setting where mundrabillaite typically forms. If you start seeing hannayite, newberyite, struvite in float, you are in the right ground. Field specimens usually show a crusts, aggregates of acicular crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find mundrabillaite on the map
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