Aliettite is a rare regular mixed-layer silicate mineral consisting of alternating talc-like and saponite-like layers. It typically forms soft, platy, or scaly masses in hydrothermal environments and is best identified through X-ray diffraction due to its macroscopic similarity to other clay minerals.
Is this aliettite?
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 aliettite with a known reference. Aliettite sits at Mohs 1-2, 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: earthy.
- 4Match the color rangeCompare against the expected color range: white, dark green, buff.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: microscopic crystals, platy.
Often confused with
Aliettite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads earthy on Aliettite and pearly, greasy, dull on Talc.
How to tell apart: Luster reads earthy on Aliettite and greasy on Saponite.
How to tell apart: Streak differs, so Aliettite leaves white, Vermiculite leaves greenish white; luster reads earthy on Aliettite and dull to pearly, bronzy on Vermiculite.
Often found alongside aliettite
Minerals reported to co-occur with aliettite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₀.₂Mg₆Si₇.₆Al₀.₄O₂₀(OH)₄·4H₂O
- Mohs hardness
- 1-2
- Density
- 2.1-2.3 g/cm³
- Colors
- Streak
- White
- Luster
- Earthy
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Microscopic crystals, platy
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- An alteration product in serpentinized ophiolites and residual in soils derived therefrom; in altered dolostones
Where rockhounds find aliettite
Classic worldwide localities
- Emilia-Romagna, at Monte Chiaro, Taro Valley, Italy
- Frassinoro, Modena, Italy
- Ferriere, Nure Valley, Italy
- Kinshasa, Katanga Province, Congo (Shaba Province, Zaire)
Field-hunting tip
Where it forms: An alteration product in serpentinized ophiolites and residual in soils derived therefrom; in altered dolostones. If you start seeing talc, chlorite, serpentine in float, you are in the right ground. Typical habit: microscopic crystals, platy. Train your eye for that shape before scanning the outcrop.
Common questions
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Find aliettite on the map
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