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. Kaolinite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Kaolinite 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.
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
- 2.6-2.68 g/cm³
- Streak
- White
- Luster
- Dull
- Transparency
- Opaque
- Crystal system
- Triclinic
- Crystal habit
- Massive
- Cleavage
- Perfect Basal
- Rarity
- Common
- Uses
- Industrial, Ceramics, Paper Filler, Cosmetics, Collector
- Host rock
- Hydrothermal Alteration Zones and Sedimentary Clay Deposits
- Typical price
- $5-20 for study specimens
Where rockhounds find kaolinite
1 mapped spotsClassic worldwide localities
- China
- USA (Georgia)
- France
- United Kingdom (Cornwall)
- Czech Republic
Field-hunting tip
Look in hydrothermal alteration zones and sedimentary clay deposits country — that is the host setting where kaolinite typically forms. If you start seeing quartz, feldspar, muscovite in float, you are in the right ground. Field specimens usually show a massive habit, so 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
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Find kaolinite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
