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. Riomarinaite leaves a white to light gray streak.
- 3Read the lusterHold the specimen under a strong light. Riomarinaite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: whitish-beige, light gray.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, radial aggregates.
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 yellow.
How to tell apart: Streak differs, so Riomarinaite leaves white to light gray, Copiapite leaves yellow; luster reads vitreous on Riomarinaite and pearly 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
- Streak
- White to Light Gray
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Platy Crystals, Radial Aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Mineral Deposits
Where rockhounds find riomarinaite
Classic worldwide localities
- Rio Marina, Elba Island, Italy
Field-hunting tip
Look in hydrothermal mineral deposits country, the host setting where riomarinaite typically forms. If you start seeing pyrite, hematite, coquimbite in float, you are in the right ground. Field specimens usually show a platy crystals, radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify riomarinaite?+
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What rocks look like riomarinaite?+
What minerals are found with riomarinaite?+
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Find riomarinaite on the map
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