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 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Gelosaite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Gelosaite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellow-green.
- 5Look at form & habitCrystal system: orthorhombic. 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: Luster reads vitreous on Gelosaite and silky on Molybdite.
How to tell apart: Lindgrenite is the harder of the two (Mohs 3 vs. 2); streak differs — Gelosaite leaves yellow, Lindgrenite leaves pale yellowish-green; luster reads vitreous on Gelosaite and pearly 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
- 2
- Density
- 3.8-3.9 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular or Fibrous Radial Aggregates
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins
- Typical price
- $50-300 per specimen
Where rockhounds find gelosaite
Classic worldwide localities
- Gelosa mine, Italy
Field-hunting tip
Look in hydrothermal veins country — that is the host setting where gelosaite typically forms. If you start seeing bismuthinite, molybdenite, quartz in float, you are in the right ground. Field specimens usually show a acicular or fibrous radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find gelosaite on the map
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