Tosudite is a complex interstratified clay mineral composed of chlorite-like and smectite-like layers. It typically forms as a soft, earthy, or platy secondary mineral in hydrothermal alteration zones and is primarily sought after by advanced collectors of clay mineral species.
Is this tosudite?
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 tosudite with a known reference. Tosudite sits at Mohs ~1, 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: nonmetallic.
- 4Match the color rangeCompare against the expected color range: white, azure, blue white, green, yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: massive.
Often confused with
Tosudite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Chlorite is the harder of the two (Mohs 2-2.5 vs. ~1); luster reads nonmetallic on Tosudite and pearly on Chlorite.
How to tell apart: Luster reads nonmetallic on Tosudite and dull, earthy on Montmorillonite.
How to tell apart: Streak differs, so Tosudite leaves white, Vermiculite leaves greenish white; luster reads nonmetallic on Tosudite and dull to pearly, bronzy on Vermiculite.
Often found alongside tosudite
Minerals reported to co-occur with tosudite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₀.₅(Al,Mg)₆(Si,Al)₈O₂₀(OH)₁₀·4H₂O
- Mohs hardness
- ~1
- Density
- 2.83 g/cm³
- Streak
- White
- Luster
- Nonmetallic
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Massive
- Cleavage
- Perfect on {001}
- Rarity
- Uncommon
- Uses
- Collector, Scientific research
- Host rock
- A hydrothermal alteration product of intermediate to felsic igneous rocks
Where rockhounds find tosudite
Classic worldwide localities
- White Mountain gold mine, Cottonwood district, Washoe Co., Nevada, USA
- Alushta, Crimea, Ukraine
- Huy, Belgium
- Ehrenfriedersdorf, Saxony, Germany
- Tooho mine, Aichi Prefecture, Japan
- Hokuno mine, Hokuno, Gifu Prefecture, Japan
Field-hunting tip
Where it forms: A hydrothermal alteration product of intermediate to felsic igneous rocks. If you start seeing rectorite, dickite, quartz in float, you are in the right ground. Typical habit: massive. Train your eye for that shape before scanning the outcrop.
Common questions
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Find tosudite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
