Bayerite is a rare polymorph of aluminum hydroxide often found in bauxite deposits and soils. It typically occurs as small, delicate, white platy crystals or fine-grained masses that are visually indistinguishable from its more common cousin, gibbsite, without laboratory analysis.
Is this bayerite?
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 bayerite with a known reference. Bayerite sits at Mohs 2.5-3, 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: white, colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, fine-grained aggregates.
Often confused with
Bayerite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside bayerite
Minerals reported to co-occur with bayerite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Al(OH)₃
- Mohs hardness
- 2.5-3
- Density
- 2.53 g/cm³
- Streak
- White
- Luster
- Pearly
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Platy crystals, fine-grained aggregates
- Cleavage
- Perfect on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Probably precipitated from high-aluminum gels on carbonates at pH > 5.8 (Hatrurim Formation, Israel); as weathered crusts on amphiboles and pyroxenes (Dnieper region, Russia); in bauxites
Where rockhounds find bayerite
Classic worldwide localities
- Hatrurim Formation, Israel
- An undefined area in the Dnieper region, and in the Listvennoye deposit, Yenisei Ridge, Siberia, Russia
- San Elias mine, San Luis Province, Argentina
- Raoul Island, Kermadec Group, South Pacific
Field-hunting tip
Where it forms: Probably precipitated from high-aluminum gels on carbonates at pH > 5.8 (Hatrurim Formation, Israel); as weathered crusts on amphiboles and pyroxenes (Dnieper region, Russia); in bauxites. If you start seeing calcite, gypsum, portlandite in float, you are in the right ground. Typical habit: platy crystals, fine-grained aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify bayerite?+
Where is bayerite found?+
What rocks look like bayerite?+
What minerals are found with bayerite?+
What kind of rock does bayerite form in?+
What is bayerite used for?+
Find bayerite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
