Brugnatellite is a rare layered double hydroxide mineral typically found as soft, platy, or micaceous aggregates. It is most commonly identified in serpentinite rocks where it forms alongside other magnesium-rich minerals in low-temperature alteration zones.
Is this brugnatellite?
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 brugnatellite with a known reference. Brugnatellite 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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly.
- 4Match the color rangeCompare against the expected color range: brown white, brownish pink, yellow brown, pink.
- 5Look at form & habitCrystal system: trigonal. Typical habit: massive, micaceous.
Often confused with
Brugnatellite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads pearly on Brugnatellite and satiny to greasy or waxy on Hydrotalcite.
How to tell apart: Luster reads pearly on Brugnatellite and waxy to vitreous, may be pearly on Pyroaurite.
How to tell apart: Streak differs, so Brugnatellite leaves white, Stichtite leaves very pale lilac to white; luster reads pearly on Brugnatellite and waxy to resinous, somewhat pearly on Stichtite.
Often found alongside brugnatellite
Minerals reported to co-occur with brugnatellite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mg₆Fe³⁺(CO₃)(OH)₁₃·4H₂O
- Mohs hardness
- ~2
- Density
- 2.14 g/cm³
- Colors
- Streak
- White
- Luster
- Pearly
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Massive, micaceous
- Cleavage
- {0001}, perfect
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- A hydrothermal alteration product in serpentinite, lining cracks with other magnesium-rich species
Where rockhounds find brugnatellite
Classic worldwide localities
- Iron Hill carbonatite, Powderhorn-Cebolla district, Gunnison Co., Colorado, USA
- Torre di Santa Maria, near Ciappanico, Val Malenco, and Monte Motta, Val Lanterna, Lombardy, Italy
- Monte Ramazzo, Borzoli, Liguria, Italy
- Viu, Val di Lanzo, Piedmont, Italy
- Bou-Offrouh, Morocco
- Swinna Ness, Unst, Shetland Islands, Scotland
Field-hunting tip
Where it forms: A hydrothermal alteration product in serpentinite, lining cracks with other magnesium-rich species. If you start seeing chrysotile, artinite, hydromagnesite in float, you are in the right ground. Typical habit: massive, micaceous. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify brugnatellite?+
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What rocks look like brugnatellite?+
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Find brugnatellite on the map
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