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, 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.
