Bracewellite is a rare chromium oxyhydroxide mineral that occurs as small, dark needle-like crystals. It is structurally related to diaspore and is typically found in association with chromite deposits within ultramafic rock environments.
Is this bracewellite?
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 bracewellite with a known reference. Bracewellite sits at Mohs 6-7, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Bracewellite leaves a brown streak.
- 3Read the lusterHold the specimen under a strong light. Bracewellite typically shows a submetallic luster.
- 4Match the color rangeCompare against the expected color range: dark brown, black.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular crystals, prismatic crystals.
Often confused with
Bracewellite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Bracewellite leaves brown, Iron Ore leaves reddish-brown to black; luster reads submetallic on Bracewellite and metallic to submetallic on Iron Ore.
How to tell apart: Streak differs, so Bracewellite leaves brown, Diaspore leaves white; luster reads submetallic on Bracewellite and vitreous on Diaspore.
Often found alongside bracewellite
Minerals reported to co-occur with bracewellite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CrO(OH)
- Mohs hardness
- 6-7
- Density
- 4.15 g/cm³
- Colors
- Streak
- Brown
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular Crystals, Prismatic Crystals
- Cleavage
- Perfect in One Direction
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Ultramafic Rocks, Hydrothermal Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find bracewellite
Classic worldwide localities
- Driekop Mine, South Africa
- Kempersai, Kazakhstan
Field-hunting tip
Look in ultramafic rocks, hydrothermal deposits country, the host setting where bracewellite typically forms. If you start seeing chromite, magnetite, goethite in float, you are in the right ground. Field specimens usually show a acicular crystals, prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find bracewellite on the map
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