Böhmite is a major constituent of bauxite ore and typically forms in low-temperature hydrothermal or sedimentary environments. It is rarely found in well-formed crystals, most often appearing as white, chalky masses, pisolites, or thin, pearly crusts within aluminum-rich sedimentary rocks.
Is this böhmite?
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 böhmite with a known reference. Böhmite sits at Mohs 3.5, 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, pearly on {010}.
- 4Match the color rangeCompare against the expected color range: white, pale grayish brown.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: pisolitic, massive, or as fibrous aggregates.
Often confused with
Böhmite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Diaspore is the harder of the two (Mohs 6.5-7 vs. 3.5); luster reads vitreous, pearly on {010} on Böhmite and adamantine, vitreous, pearly on cleavage faces on Diaspore.
How to tell apart: Böhmite is noticeably harder (Mohs 3.5 vs. 2-2.5); luster reads vitreous, pearly on {010} on Böhmite and pearly to dull earthy on Kaolinite.
Often found alongside böhmite
Minerals reported to co-occur with böhmite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- γ-AlO(OH)
- Mohs hardness
- 3.5
- Density
- 3.02-3.05 g/cm³
- Colors
- WhitePale grayish brown
- Streak
- White
- Luster
- Vitreous, pearly on {010}
- Transparency
- Semitransparent
- Crystal system
- Orthorhombic
- Crystal habit
- Pisolitic, massive, or as fibrous aggregates
- Cleavage
- {010}, very good; {100}, well-developed; {001}, poor
- Rarity
- Common
- Uses
- Industrial, Collector
- Host rock
- Formed from aluminosilicates during tropical weathering, commonly a major constituent of bauxites, laterites, or fireclays
Where rockhounds find böhmite
Classic worldwide localities
- Alberhill clay pits, Riverside Co., California, USA
- Linwood-Barton district, and at the Laurel Creek mine, Rabun Co., Georgia, USA
- Hogback Mountain, Jackson Co., North Carolina, USA
- Les Baux, near Arles, Bouches-du-Rhône, France
- Recoux, Var, France
- Pérlille and Cadarcet, Ariège, France
Field-hunting tip
Where it forms: Formed from aluminosilicates during tropical weathering, commonly a major constituent of bauxites, laterites, or fireclays. If you start seeing kaolinite, gibbsite, diaspore in float, you are in the right ground. Typical habit: pisolitic, massive, or as fibrous aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify böhmite?+
Where is böhmite found?+
What rocks look like böhmite?+
What minerals are found with böhmite?+
What kind of rock does böhmite form in?+
What is böhmite used for?+
Find böhmite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
