Spheniscidite is a rare phosphate mineral typically found as secondary crusts or fine platy crystals in guano-rich environments. Collectors usually find it as white to yellow earthy aggregates associated with other phosphate minerals in oceanic island deposits.
Is this spheniscidite?
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 spheniscidite with a known reference. Spheniscidite 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. Spheniscidite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Spheniscidite typically shows a dull to earthy luster.
- 4Match the color rangeCompare against the expected color range: colorless, brownish.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, crusts, pulverulent.
Often confused with
Spheniscidite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Spheniscidite is noticeably harder (Mohs 2 vs. 1); luster reads dull to earthy on Spheniscidite and pearly on Taranakite.
How to tell apart: Leucophosphite is the harder of the two (Mohs 3.5 vs. 2); luster reads dull to earthy on Spheniscidite and vitreous to waxy on Leucophosphite.
Often found alongside spheniscidite
Minerals reported to co-occur with spheniscidite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (NH₄)(Fe³⁺,Al)₂(PO₄)₂(OH)·2H₂O
- Mohs hardness
- 2
- Density
- 2.71 g/cm³
- Streak
- White
- Luster
- Dull to Earthy
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Platy Crystals, Crusts, Pulverulent
- Cleavage
- Perfect On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Guano Deposits On Island Rocks
Where rockhounds find spheniscidite
Classic worldwide localities
- Elephant Island, about 800 km southeast of Cape Horn, British Antarctic Territory, Antarctica
Field-hunting tip
Look in guano deposits on island rocks country, the host setting where spheniscidite typically forms. If you start seeing leucophosphite, taranakite, ammonia-stromeyerite in float, you are in the right ground. Field specimens usually show a platy crystals, crusts, pulverulent habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify spheniscidite?+
Where is spheniscidite found?+
What rocks look like spheniscidite?+
What minerals are found with spheniscidite?+
What kind of rock does spheniscidite form in?+
What is spheniscidite used for?+
Find spheniscidite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
