Rodolicoite is a rare iron phosphate mineral that typically occurs as small crystals or aggregates within granite pegmatites. It is often identified by its association with altered triphylite and its trigonal crystal structure, which is homeotypic to quartz. Collectors prize it as a rare mineralogical find from specific phosphatic pegmatite localities.
Is this rodolicoite?
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 rodolicoite with a known reference. Rodolicoite sits at Mohs 5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brown.
- 3Read the lusterHold the specimen under a strong light. Luster: greasy.
- 4Match the color rangeCompare against the expected color range: brown, red brown.
- 5Look at form & habitCrystal system: trigonal. Typical habit: aggregates, nodular.
Often confused with
Rodolicoite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Quartz is the harder of the two (Mohs 7 vs. 5); streak differs, so Rodolicoite leaves brown, Quartz leaves white; luster reads greasy on Rodolicoite and vitreous; waxy to dull when massive on Quartz.
How to tell apart: Berlinite is the harder of the two (Mohs ~6.5 vs. 5); streak differs, so Rodolicoite leaves brown, Berlinite leaves white; luster reads greasy on Rodolicoite and vitreous on Berlinite.
Often found alongside rodolicoite
Minerals reported to co-occur with rodolicoite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- FePO₄
- Mohs hardness
- 5
- Density
- 3.07 g/cm³
- Streak
- Brown
- Luster
- Greasy
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Aggregates, nodular
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Very rare, in microcrystalline nodules in lignite beds which appear to have naturally burned
Where rockhounds find rodolicoite
Classic worldwide localities
- Castelnuovo mine, Santa Barbara lignite district, 30 km southeast of Florence, Florence, Italy
Field-hunting tip
Where it forms: Very rare, in microcrystalline nodules in lignite beds which appear to have naturally burned. If you start seeing grattarolaite, heterosite in float, you are in the right ground. Typical habit: aggregates, nodular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify rodolicoite?+
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What rocks look like rodolicoite?+
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Find rodolicoite on the map
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