Oxammite is an extremely rare organic mineral found primarily in guano deposits on islands where it forms through the reaction of bird excrement with phosphate-rich environments. It typically appears as white, crumbly crusts or small crystalline efflorescences that are highly susceptible to dissolution in water or humidity.
Is this oxammite?
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 oxammite with a known reference. Oxammite sits at Mohs 2.5, 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: colorless, yellowish white.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: crusts, efflorescences, or tiny granular aggregates.
Often confused with
Oxammite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside oxammite
Minerals reported to co-occur with oxammite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (NH₄)₂C₂O₄·H₂O
- Mohs hardness
- 2.5
- Density
- 1.5 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Crusts, efflorescences, or tiny granular aggregates
- Cleavage
- On {001}, distinct
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Derived from bird or bat guano; in subfossil bird eggs and on subfossil birds
Where rockhounds find oxammite
Classic worldwide localities
- Guañape Islands, south of Trujillo, Peru
- Petrogale Cave, near Madura, Western Australia
- Hamar an Nafur Island, Gulf of Masirah, Oman
Field-hunting tip
Where it forms: Derived from bird or bat guano; in subfossil bird eggs and on subfossil birds. If you start seeing mascagnite in float, you are in the right ground. Typical habit: crusts, efflorescences, or tiny granular aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify oxammite?+
Where is oxammite found?+
What rocks look like oxammite?+
What minerals are found with oxammite?+
What kind of rock does oxammite form in?+
What is oxammite used for?+
Find oxammite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
