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, 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.