Riomarinaite is a rare bismuth sulfate, typically whitish-beige to light gray. It is a weathering product from the decomposition of bismuthinite and cosalite. It was first described from Falcacci stope, Rio Marina iron mine, east coast of Elba Island, Tuscany, Italy.
Is this riomarinaite?
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 riomarinaite with a known reference. Riomarinaite sits at Mohs 2-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white to light gray.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: light beige, light gray.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: botryoidal, encrustations.
Often confused with
Riomarinaite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Riomarinaite leaves white to light gray, Jarosite leaves pale yellow; luster reads vitreous on Riomarinaite and subadamantine to vitreous, resinous on fractures on Jarosite.
How to tell apart: Streak differs, so Riomarinaite leaves white to light gray, Copiapite leaves pale yellow; luster reads vitreous on Riomarinaite and pearly on {010} on Copiapite.
Often found alongside riomarinaite
Minerals reported to co-occur with riomarinaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Bi(SO₄)(OH)·H₂O
- Mohs hardness
- 2-3
- Density
- 4.80 g/cm³
- Colors
- Light beigeLight gray
- Streak
- White to light gray
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Botryoidal, encrustations
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A weathering product from the decomposition of bismuthinite and cosalite
Where rockhounds find riomarinaite
Classic worldwide localities
- Falcacci stope, Rio Marina iron mine, east coast of Elba Island, Tuscany, Italy
Field-hunting tip
Where it forms: A weathering product from the decomposition of bismuthinite and cosalite. If you start seeing bismoclite, bismutite, cannonite in float, you are in the right ground. Typical habit: botryoidal, encrustations. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify riomarinaite?+
Where is riomarinaite found?+
What rocks look like riomarinaite?+
What minerals are found with riomarinaite?+
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Find riomarinaite on the map
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