Ferruccite is a very rare sodium fluoroborate mineral typically found in volcanic fumaroles. It most commonly appears as small, colorless to white tabular crystals or thin crusts in proximity to other borate minerals.
Is this ferruccite?
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 ferruccite with a known reference. Ferruccite 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: vitreous.
- 4Match the color rangeCompare against the expected color range: colorless, white.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: tabular crystals, crystalline crusts.
Often confused with
Ferruccite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside ferruccite
Minerals reported to co-occur with ferruccite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaBF₄
- Mohs hardness
- ~3
- Density
- 2.496 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Tabular crystals, crystalline crusts
- Cleavage
- {100}, {010}, and {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As a fumarolic sublimate
Where rockhounds find ferruccite
Classic worldwide localities
- Vesuvius, Campania, and on Vucano, Aeolian Islands, Italy
- Volcanoes on the Kamchatka Peninsula, Russia
Field-hunting tip
Where it forms: As a fumarolic sublimate. If you start seeing sassolite, fluorborates, fluorsilicates in float, you are in the right ground. Typical habit: tabular crystals, crystalline crusts. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ferruccite?+
Where is ferruccite found?+
What rocks look like ferruccite?+
What minerals are found with ferruccite?+
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What is ferruccite used for?+
Find ferruccite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
