Gelosaite is an extremely rare secondary bismuth molybdate mineral typically found as delicate, fibrous yellow crystal sprays. It was first identified in the Gelosa mine in Italy, occurring in oxidized zones of hydrothermal ore deposits. Due to its scarcity and fragile crystal habit, it is highly sought after by advanced mineral collectors.
Is this gelosaite?
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 gelosaite with a known reference. Gelosaite sits at Mohs ~3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine.
- 4Match the color rangeCompare against the expected color range: yellow, colorless, yellowish green, pale blue.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular or fibrous radial aggregates.
Often confused with
Gelosaite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Gelosaite is noticeably harder (Mohs ~3 vs. 1-2); streak differs, so Gelosaite leaves white, Ferrimolybdite leaves pale yellow.
How to tell apart: Lindgrenite is the harder of the two (Mohs 4.5 vs. ~3); streak differs, so Gelosaite leaves white, Lindgrenite leaves light green; luster reads adamantine on Gelosaite and greasy on Lindgrenite.
Often found alongside gelosaite
Minerals reported to co-occur with gelosaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Bi₂(MoO₄)₃·nH₂O
- Mohs hardness
- ~3
- Density
- 5.114 g/cm³
- Streak
- White
- Luster
- Adamantine
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular or fibrous radial aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral formed in the oxidation zone of bismuth-molybdenum deposits
Where rockhounds find gelosaite
Classic worldwide localities
- Gelosa mine, Italy
Field-hunting tip
Where it forms: A secondary mineral formed in the oxidation zone of bismuth-molybdenum deposits. If you start seeing sardignaite, ferrimolybdite, koechlinite in float, you are in the right ground. Typical habit: acicular or fibrous radial aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify gelosaite?+
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Find gelosaite on the map
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