Larderellite is an extremely rare ammonium borate mineral found almost exclusively in volcanic fumarole environments. It typically forms delicate, white, pearly bladed crystals or radiating aggregates that are highly sensitive to humidity and thermal degradation.
Is this larderellite?
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 larderellite with a known reference. Larderellite sits at Mohs 1-2, 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: pearly.
- 4Match the color rangeCompare against the expected color range: white, yellowish.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: bladed crystals, radial aggregates, crusts.
Often confused with
Larderellite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside larderellite
Minerals reported to co-occur with larderellite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NH₄B₅O₇(OH)₂·H₂O
- Mohs hardness
- 1-2
- Density
- 1.905 g/cm³
- Streak
- White
- Luster
- Pearly
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Bladed crystals, radial aggregates, crusts
- Cleavage
- On {100}, {010}, perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In boric-acid-rich fumarolic lagoons
Where rockhounds find larderellite
Classic worldwide localities
- Larderello, Val di Cecina, Tuscany, Italy
Field-hunting tip
Where it forms: In boric-acid-rich fumarolic lagoons. If you start seeing sassolite, ammonioborite, santite in float, you are in the right ground. Typical habit: bladed crystals, radial aggregates, crusts. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify larderellite?+
Where is larderellite found?+
What rocks look like larderellite?+
What minerals are found with larderellite?+
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Find larderellite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
