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.

Hardness

1.5-2

Mohs

Luster

Pearly

Streak

White

Transparency

Translucent

mineraluncommonChlorite-Smectite Mixed Layer Group family

Tosudite

Hardness: 1.5-2
Luster: Pearly
Streak: White
Transparency: Translucent

Is this tosudite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch tosudite with a known reference. Tosudite sits at Mohs 1.5-2 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Tosudite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Tosudite typically shows a pearly luster.
4
Match the color range
Compare against the expected color range: white, gray, yellow, greenish.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: platy crystals, massive, fine-grained aggregates.

Often confused with

Tosudite vs. its common look-alikes — and how to tell them apart in the field.

How to tell apart: Luster reads pearly on Tosudite and dull on Montmorillonite.

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: 1.5-2
Density: 2.3-2.6 g/cm³
Colors: White Gray Yellow Greenish
Streak: White
Luster: Pearly
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Platy Crystals, Massive, Fine-grained Aggregates
Cleavage: Perfect Basal
Rarity: Uncommon
Uses: Collector, Scientific Research
Host rock: Hydrothermal Veins, Alteration Zones of Clay Deposits
Typical price: $20-80 for small cabinet specimens

Where rockhounds find tosudite

Classic worldwide localities

Tosudo, Japan
Urals, Russia
Kazakhstan
France

Field-hunting tip

Look in hydrothermal veins, alteration zones of clay deposits country — that is the host setting where tosudite typically forms. If you start seeing quartz, pyrite, kaolinite in float, you are in the right ground. Field specimens usually show a platy crystals, massive, fine-grained aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify tosudite?+

Mohs hardness is 1.5-2. It typically shows a pearly luster. The streak is white. Common colors include white, gray, yellow, greenish.

Where is tosudite found?+

Notable localities include Tosudo, Japan; Urals, Russia; Kazakhstan; France.

How much is tosudite worth?+

Typical asking prices fall in the range of $20-80 for small cabinet specimens. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like tosudite?+

Tosudite is most often confused with Chlorite, Montmorillonite, Vermiculite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with tosudite?+

Tosudite commonly co-occurs with Quartz, Pyrite, Kaolinite, Dickite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does tosudite form in?+

Tosudite typically forms in hydrothermal veins, alteration zones of clay deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is tosudite used for?+

Tosudite is used in collector, scientific research.

Find tosudite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.