Kaolin is a soft, earthy, white clay mineral that is usually formed by the chemical weathering of aluminum-rich silicate minerals like feldspar. Collectors typically find it in massive, powdery, or plastic clay-like deposits rather than distinct crystals. It is essential for the production of porcelain and high-quality paper, often occurring in large sedimentary basins or altered granite deposits.
Is this kaolin?
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 kaolin with a known reference. Kaolin sits at Mohs 2-2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Kaolin leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Kaolin typically shows a dull luster.
- 4Match the color rangeCompare against the expected color range: white, grayish, yellowish, brownish.
- 5Look at form & habitCrystal system: triclinic. Typical habit: massive, earthy, clay-like, sometimes microscopic plates.
Often confused with
Kaolin vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside kaolin
Minerals reported to co-occur with kaolin. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Al₂Si₂O₅(OH)₄
- Mohs hardness
- 2-2.5
- Density
- 2.6-2.65 g/cm³
- Streak
- White
- Luster
- Dull
- Transparency
- Opaque
- Crystal system
- Triclinic
- Crystal habit
- Massive, Earthy, Clay-like, Sometimes Microscopic Plates
- Cleavage
- Perfect Basal
- Rarity
- Common
- Uses
- Industrial, Ceramic Manufacture, Paper Filler, Cosmetics
- Host rock
- Hydrothermal Altered Igneous Rocks, Sedimentary Beds From Weathered Feldspar
- Typical price
- $5-20 for bulk samples
Where rockhounds find kaolin
1 mapped spotsClassic worldwide localities
- Cornwall, England
- Georgia, USA
- Limousin, France
- Saxony, Germany
- Brazil
Field-hunting tip
Look in hydrothermal altered igneous rocks, sedimentary beds from weathered feldspar country, the host setting where kaolin typically forms. If you start seeing quartz, feldspar, mica in float, you are in the right ground. Field specimens usually show a massive, earthy, clay-like, sometimes microscopic plates habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Arizona. Start trip planning there.
Common questions
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Find kaolin on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
