Santabarbaraite is a rare, amorphous hydrated iron phosphate mineral typically found as earthy crusts or nodules. It is often a secondary alteration product resulting from the oxidation of vivianite, occurring most famously in the Santa Barbara mine in Italy. Collectors usually identify it by its dull, brown appearance and association with vivianite remnants.
Is this santabarbaraite?
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 santabarbaraite with a known reference. Santabarbaraite 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. Santabarbaraite leaves a amber streak.
- 3Read the lusterHold the specimen under a strong light. Santabarbaraite typically shows a vitreous to greasy luster.
- 4Match the color rangeCompare against the expected color range: brown, yellowish-brown, dark brown.
- 5Look at form & habitCrystal system: amorphous. Typical habit: crusts, masses, earthy aggregates.
Often confused with
Santabarbaraite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Santabarbaraite leaves amber, Vivianite leaves white to light blue; luster reads vitreous to greasy on Santabarbaraite and vitreous on Vivianite.
How to tell apart: Strengite is the harder of the two (Mohs 3.5-4 vs. 2.5); streak differs, so Santabarbaraite leaves amber, Strengite leaves white; luster reads vitreous to greasy on Santabarbaraite and vitreous on Strengite.
Often found alongside santabarbaraite
Minerals reported to co-occur with santabarbaraite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe₃(PO₄)₂(OH)₃·5H₂O
- Mohs hardness
- 2.5
- Density
- 2.42 g/cm³
- Streak
- Amber
- Luster
- Vitreous to Greasy
- Transparency
- Translucent
- Crystal system
- Amorphous
- Crystal habit
- Crusts, Masses, Earthy Aggregates
- Cleavage
- None, Good Parting Along The {010} Cleavage of The Vivianite Precursor
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Iron-rich Ore Deposits
Where rockhounds find santabarbaraite
Classic worldwide localities
- Santa Barbara mine, Tuscany, Italy
- Big Fish River, Yukon, Canada
- various iron-rich sedimentary deposits
Field-hunting tip
Look in oxidized zones of iron-rich ore deposits country, the host setting where santabarbaraite typically forms. If you start seeing vivianite, goethite, lepidocrocite in float, you are in the right ground. Field specimens usually show a crusts, masses, earthy aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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What rocks look like santabarbaraite?+
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Find santabarbaraite on the map
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