Phosphammite is a rare ammonium phosphate mineral that typically forms as a secondary mineral in guano deposits. It is highly soluble and hygroscopic, meaning it should be stored in a dry, sealed container to prevent deliquescence.
Is this phosphammite?
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 phosphammite with a known reference. Phosphammite sits at Mohs 1.5-2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Phosphammite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Phosphammite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, yellowish.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: crusts, granular, powdery aggregates.
Often confused with
Phosphammite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside phosphammite
Minerals reported to co-occur with phosphammite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (NH₄)₂HPO₄
- Mohs hardness
- 1.5-2
- Density
- 1.84 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Crusts, Granular, Powdery Aggregates
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Guano Deposits in Arid Caves or Island Environments
- Typical price
- $20-100 for small specimens
Where rockhounds find phosphammite
Classic worldwide localities
- Guaiave Island (Venezuela)
- Chincha Islands (Peru)
- various guano deposits
Field-hunting tip
Look in guano deposits in arid caves or island environments country — that is the host setting where phosphammite typically forms. If you start seeing mascagnite, boussingaultite, taranakite in float, you are in the right ground. Field specimens usually show a crusts, granular, powdery aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find phosphammite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
