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. Streak: amber.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to greasy.
- 4Match the color rangeCompare against the expected color range: brown, light brown.
- 5Look at form & habitCrystal system: amorphous. Typical habit: aggregates, pseudomorphous.
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, altering to dark blue, brown.
How to tell apart: Strengite is the harder of the two (Mohs 3.5 vs. 2.5); streak differs, so Santabarbaraite leaves amber, Strengite leaves white.
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
- Colors
- Streak
- Amber
- Luster
- Vitreous to greasy
- Transparency
- Translucent
- Crystal system
- Amorphous
- Crystal habit
- Aggregates, pseudomorphous
- Cleavage
- None, good parting along the {010} cleavage of the vivianite precursor
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In cavities within concretionary nodules, in clays in a clastic rock sequence (Italy) and in clay underlying basalt (Australia)
Where rockhounds find santabarbaraite
Classic worldwide localities
- Valdarno Superiore, Upper Arno River Valley, Tuscany, Italy and Wannon Falls, ~7 km west of Hamilton, Victoria, Australia
Field-hunting tip
Where it forms: In cavities within concretionary nodules, in clays in a clastic rock sequence (Italy) and in clay underlying basalt (Australia). If you start seeing vivianite, metavivianite, clay in float, you are in the right ground. Typical habit: aggregates, pseudomorphous. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify santabarbaraite?+
Where is santabarbaraite found?+
What rocks look like santabarbaraite?+
What minerals are found with santabarbaraite?+
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What is santabarbaraite used for?+
Find santabarbaraite on the map
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