Stevensite is a rare, magnesium-rich member of the smectite clay group, typically forming as a secondary alteration product. It is characterized by its soft, soapy feel and dense, compact massive habit rather than visible crystals. Collectors often find it in evaporite deposits or as a replacement product in ultramafic rocks.

Hardness

1-2

Mohs

Luster

Dull

Streak

White

Transparency

Opaque

mineraluncommonSmectite Group family

Stevensite

Hardness: 1-2
Luster: Dull
Streak: White
Transparency: Opaque

Is this stevensite?

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 stevensite with a known reference. Stevensite sits at Mohs 1-2 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Stevensite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Stevensite typically shows a dull luster.
4
Match the color range
Compare against the expected color range: white, gray, yellowish, pinkish.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: massive.

Often confused with

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

How to tell apart: Luster reads dull on Stevensite and pearly on Talc.

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Often found alongside stevensite

Minerals reported to co-occur with stevensite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Na₀.₃Mg₃Si₄O₁₀(OH)₂·n(H₂O)
Mohs hardness: 1-2
Density: 2.0-2.2 g/cm³
Colors: White Gray Yellowish Pinkish
Streak: White
Luster: Dull
Transparency: Opaque
Crystal system: Monoclinic
Crystal habit: Massive
Cleavage: None
Rarity: Uncommon
Uses: Collector, Scientific Research
Host rock: Sedimentary Basins and Alteration Zones of Magnesium-rich Rocks
Typical price: $10-40 per specimen

Where rockhounds find stevensite

Classic worldwide localities

Stevens Canyon, New Jersey, USA
Amargosa Valley, Nevada, USA
Kizil-Dere, Azerbaijan
Akhaten, Mongolia

Field-hunting tip

Look in sedimentary basins and alteration zones of magnesium-rich rocks country — that is the host setting where stevensite typically forms. If you start seeing calcite, dolomite, serpentine in float, you are in the right ground. Field specimens usually show a massive habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify stevensite?+

Mohs hardness is 1-2. It typically shows a dull luster. The streak is white. Common colors include white, gray, yellowish, pinkish.

Where is stevensite found?+

Notable localities include Stevens Canyon, New Jersey, USA; Amargosa Valley, Nevada, USA; Kizil-Dere, Azerbaijan; Akhaten, Mongolia.

How much is stevensite worth?+

Typical asking prices fall in the range of $10-40 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like stevensite?+

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

What minerals are found with stevensite?+

Stevensite commonly co-occurs with Calcite, Dolomite, Serpentine. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does stevensite form in?+

Stevensite typically forms in sedimentary basins and alteration zones of magnesium-rich rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is stevensite used for?+

Stevensite is used in collector, scientific research.

Find stevensite on the map

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