Dickite is a polymorph of kaolinite and is often found as a white, fine-grained, clay-like material or as distinct, platy micro-crystals. Collectors often find it in hydrothermal veins associated with metallic ores or as a constituent of sedimentary clay beds. It is best identified through X-ray diffraction, as it is visually indistinguishable from other clay minerals to the naked eye.
Is this dickite?
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 dickite with a known reference. Dickite 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: satiny.
- 4Match the color rangeCompare against the expected color range: white, blue, colorless, gray, yellow brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: earthy.
Often confused with
Dickite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads satiny on Dickite and pearly to dull earthy on Kaolinite.
How to tell apart: Luster reads satiny on Dickite and pearly on Nacrite.
How to tell apart: Dickite is noticeably harder (Mohs 2-2.5 vs. 1); luster reads satiny on Dickite and pearly, greasy, dull on Talc.
Often found alongside dickite
Minerals reported to co-occur with dickite. 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
- 2.60 g/cm³
- Streak
- White
- Luster
- Satiny
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Earthy
- Cleavage
- Perfect on {001}
- Rarity
- Common
- Uses
- Collector, Industrial
- Host rock
- Commonly of hydrothermal origin along veins derived in part from the alteration of aluminosilicate minerals; also as an authigenic sedimentary mineral
Where rockhounds find dickite
2 mapped spotsClassic worldwide localities
- Red Mountain, near Ouray, San Juan Co., Colorado, USA
- Mineral Mountain area, near St. George, Washington Co., Utah, USA
- Pine Knot colliery, Schuylkill, Schuylkill Co., Pennsylvania, USA
- Bruin Creek, Elliott Co., Kentucky, USA
- Some localities for studied materials follow: at Amlwch and the Pant-y-Gaseg quarry, Trwynbychan, Anglesey, Wales
- Mád, Hungary
Field-hunting tip
Where it forms: Commonly of hydrothermal origin along veins derived in part from the alteration of aluminosilicate minerals; also as an authigenic sedimentary mineral. If you start seeing quartz, chalcedony 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 Missouri, Wisconsin. Start trip planning there.
Common questions
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Find dickite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
