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 — that is 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.
