Leguernite is a rare bismuth sulfate that forms colorless to white acicular crystals. It is a sublimate on volcanic rock from the walls of a high-temperature fumarole. It was first described from Fumarole FF, La Fossa crater, Vulcano, Aeolian Islands, Italy.
Is this leguernite?
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 leguernite with a known reference. Leguernite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Leguernite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Leguernite typically shows a subadamantine luster.
- 4Match the color rangeCompare against the expected color range: colorless, white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular crystals.
Often confused with
Leguernite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Leguernite leaves white, Autunite leaves pale yellow; luster reads subadamantine on Leguernite and pearly on Autunite.
How to tell apart: Streak differs, so Leguernite leaves white, Uranophane leaves yellowish white; luster reads subadamantine on Leguernite and vitreous on Uranophane.
Often found alongside leguernite
Minerals reported to co-occur with leguernite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Bi₁₂.₆₇O₁₄(SO₄)₅
- Mohs hardness
- 2.5
- Density
- 7.375 g/cm³
- Streak
- White
- Luster
- Subadamantine
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular Crystals
- Cleavage
- None
- Fluorescence
- Bright Green Under UV Light
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Uranium-bearing Hydrothermal Veins
Where rockhounds find leguernite
Classic worldwide localities
- Fumarole FF, Aeolian Islands, Italy
Field-hunting tip
Look in uranium-bearing hydrothermal veins country, the host setting where leguernite typically forms. If you start seeing uraninite, pyromorphite in float, you are in the right ground. Field specimens usually show a acicular crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify leguernite?+
Where is leguernite found?+
Is leguernite safe to handle?+
What rocks look like leguernite?+
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Find leguernite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
