Kaolinite is a soft, earthy, white clay mineral that is usually found in massive or clay-like aggregates. It is formed primarily through the chemical weathering or hydrothermal alteration of aluminum-silicate minerals like feldspar. Collectors often seek out specimens associated with other minerals in pockets or clay-filled voids.
Is this kaolinite?
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 kaolinite with a known reference. Kaolinite 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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly to dull earthy.
- 4Match the color rangeCompare against the expected color range: white, brownish white, grayish white, yellowish white, grayish green.
- 5Look at form & habitCrystal system: triclinic. Typical habit: earthy.
Often confused with
Kaolinite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside kaolinite
Minerals reported to co-occur with kaolinite. 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
- 2.61-2.68 g/cm³
- Streak
- White
- Luster
- Pearly to dull earthy
- Transparency
- Transparent to translucent as single crystals
- Crystal system
- Triclinic
- Crystal habit
- Earthy
- Cleavage
- Perfect on {001}
- Rarity
- Common
- Uses
- Industrial, Ceramics, Paper filler, Cosmetics, Collector
- Host rock
- Replaces other aluminosilicate minerals during hydrothermal alteration and weathering
Where rockhounds find kaolinite
1 mapped spotsClassic worldwide localities
- Macon, Bibb Co., Georgia, USA
- Dixie Clay Company mine, and in the Lamar Pit, near Bath, Aikin Co., South Carolina, USA
- Webster, Jackson Co., North Carolina, USA
- Murfreesboro, Pike Co., and at Greenwood, Sebastian Co., Arkansas, USA
- Kauling, Kiangsi Province, China
- Limoges, Haute-Vienne, France
Field-hunting tip
Where it forms: Replaces other aluminosilicate minerals during hydrothermal alteration and weathering. If you start seeing quartz, feldspar, muscovite in float, you are in the right ground. Typical habit: earthy. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah. Start trip planning there.
Common questions
How do you identify kaolinite?+
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Can I find kaolinite in the United States?+
What rocks look like kaolinite?+
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Find kaolinite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
