Brumadoite is a rare copper selenite mineral found primarily in the magnesite mines of Bahia, Brazil. It typically appears as small, bright yellow to greenish-yellow tabular crystals or radiating sprays within vugs and fractures. Collectors prize it for its unique chemistry and association with rare selenium-bearing species.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Brumadoite

Hardness: 3
Luster: Vitreous
Streak: White
Transparency: Transparent

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Is this brumadoite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch brumadoite with a known reference. Brumadoite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Brumadoite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Brumadoite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: yellow, greenish-yellow.
5
Look at form & habit
Crystal 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.

mineral

Chalcomenite

Mohs 2.5

How to tell apart: Streak differs, so Brumadoite leaves white, Chalcomenite leaves pale blue.

How to tell apart: Streak differs, so Brumadoite leaves white, Malachite leaves light green.

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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(SeO₃)₂(OH)₄
Mohs hardness: 3
Density: 4.8 g/cm³
Colors: Yellow Greenish-yellow
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Tabular Crystals, Radiating Aggregates
Cleavage: Good
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Veins in Magnesite Deposits
Typical price: $50-500 depending on specimen size and clarity

Where rockhounds find brumadoite

Classic worldwide localities

Brumado, Bahia, Brazil

Field-hunting tip

Look in hydrothermal veins in magnesite deposits country, the host setting where brumadoite typically forms. If you start seeing chalcomenite, magnesite, dolomite in float, you are in the right ground. Field specimens usually show a tabular crystals, radiating aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify brumadoite?+

Mohs hardness is 3. It typically shows a vitreous luster. The streak is white. Common colors include yellow, greenish-yellow.

Where is brumadoite found?+

Notable localities include Brumado, Bahia, Brazil.

How much is brumadoite worth?+

Typical asking prices fall in the range of $50-500 depending on specimen size and clarity. Quality, size, and provenance can move individual specimens well outside that range.

Is brumadoite safe to handle?+

It contains toxic constituents. Contains copper and selenium; wash hands thoroughly after handling and avoid inhaling dust. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like brumadoite?+

Brumadoite is most often confused with Chalcomenite, Malachite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with brumadoite?+

Brumadoite commonly co-occurs with Chalcomenite, Magnesite, Dolomite, Quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does brumadoite form in?+

Brumadoite typically forms in hydrothermal veins in magnesite deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is brumadoite used for?+

Brumadoite is used in collector.

Find brumadoite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.