Brumadoite is a rare copper tellurium hydroxide, typically blue. It is a late fracture-filling mineral in coarse-grained magnesite. Associated minerals include magnesite, mottramite and quartz. It was first described from Pedra Preta mine, Serra das Éguas, Brumado, Bahia, Brazil.
Is this brumadoite?
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 brumadoite with a known reference. Brumadoite 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: pale blue.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: blue.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, radiating aggregates.
Often confused with
Brumadoite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Brumadoite leaves pale blue, Chalcomenite leaves light blue.
How to tell apart: Luster reads vitreous on Brumadoite and adamantine to vitreous; silky if fibrous; dull to earthy if massive on Malachite.
Often found alongside brumadoite
Minerals reported to co-occur with brumadoite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₃(Te⁶⁺O₄)(OH)₄·5H₂O
- Mohs hardness
- 3
- Density
- 2.60 g/cm³
- Colors
- Streak
- Pale blue
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular crystals, radiating aggregates
- Cleavage
- None observed
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A late fracture-filling mineral in coarse-grained magnesite
Where rockhounds find brumadoite
Classic worldwide localities
- Pedra Preta mine, Serra das Éguas, Brumado, Bahia, Brazil
Field-hunting tip
Where it forms: A late fracture-filling mineral in coarse-grained magnesite. If you start seeing magnesite, mottramite, quartz in float, you are in the right ground. Typical habit: tabular crystals, radiating aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
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Find brumadoite on the map
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