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 1-1.5, 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: dull, earthy.
- 4Match the color rangeCompare against the expected color range: brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: selvage.
Often confused with
Spheniscidite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads dull, earthy on Spheniscidite and pearly on Taranakite.
How to tell apart: Leucophosphite is the harder of the two (Mohs 3.5 vs. 1-1.5); luster reads dull, earthy on Spheniscidite and vitreous to waxy, chalky on Leucophosphite.
All properties
- Chemical formula
- (NH₄)Fe₂(PO₄)₂(OH)(H₂O)·H₂O
- Mohs hardness
- 1-1.5
- Density
- 2.71 g/cm³
- Colors
- Streak
- White
- Luster
- Dull, earthy
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Selvage
- Cleavage
- Perfect on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Formed by interaction of phosphate solutions derived from guano with micaceous and chloritic minerals in soil under a penguin rookery
Where rockhounds find spheniscidite
Classic worldwide localities
- Elephant Island, South Shetland Islands, about 800 km southeast of Cape Horn, British Antarctic Territory, Antarctica
Field-hunting tip
Where it forms: Formed by interaction of phosphate solutions derived from guano with micaceous and chloritic minerals in soil under a penguin rookery. If you start seeing micas, chlorites in float, you are in the right ground. Typical habit: selvage. 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.
