Prewittite is an extremely rare secondary mineral found in the high-temperature volcanic fumaroles of the Tolbachik volcano in Russia. It typically forms as small, striking orange-red tabular crystals associated with other rare selenium-bearing minerals.

Hardness

2-3

Mohs

Luster

Adamantine

Streak

Yellowish-orange

Transparency

Translucent

mineralrare

Prewittite

Hardness: 2-3
Luster: Adamantine
Streak: Yellowish-orange
Transparency: Translucent

No image

Is this prewittite?

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 prewittite with a known reference. Prewittite sits at Mohs 2-3 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Prewittite leaves a yellowish-orange streak.
3
Read the luster
Hold the specimen under a strong light. Prewittite typically shows a adamantine luster.
4
Match the color range
Compare against the expected color range: orange, orange-red.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular to blocky crystals.

Often confused with

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

mineral

Klyuchevskite

Mohs 2-2.5

How to tell apart: Streak differs — Prewittite leaves yellowish-orange, Klyuchevskite leaves white; luster reads adamantine on Prewittite and vitreous on Klyuchevskite.

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Often found alongside prewittite

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

All properties

Chemical formula: KPb₁.5Cu(SeO₃)₂Cl(OH)₂
Mohs hardness: 2-3
Density: 4.26 g/cm³
Colors: Orange Orange-red
Streak: Yellowish-orange
Luster: Adamantine
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Tabular to Blocky Crystals
Cleavage: Perfect On {001}
Rarity: Rare
Uses: Collector
Host rock: Fumarole Deposits
Typical price: $200-1000+ per specimen

Where rockhounds find prewittite

Classic worldwide localities

Tolbachik volcano, Kamchatka Peninsula, Russia

Field-hunting tip

Look in fumarole deposits country — that is the host setting where prewittite typically forms. If you start seeing sylvite, halite, tenorite in float, you are in the right ground. Field specimens usually show a tabular to blocky crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify prewittite?+

Mohs hardness is 2-3. It typically shows a adamantine luster. The streak is yellowish-orange. Common colors include orange, orange-red.

Where is prewittite found?+

Notable localities include Tolbachik volcano, Kamchatka Peninsula, Russia.

How much is prewittite worth?+

Typical asking prices fall in the range of $200-1000+ per specimen. Quality, size, and provenance can move individual specimens well outside that range.

Is prewittite safe to handle?+

It contains toxic constituents. Contains lead, copper, and selenium. Wash hands thoroughly after handling and avoid inhaling dust or powder. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like prewittite?+

Prewittite is most often confused with Klyuchevskite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with prewittite?+

Prewittite commonly co-occurs with Sylvite, Halite, Tenorite, Langbeinite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does prewittite form in?+

Prewittite typically forms in fumarole deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is prewittite used for?+

Prewittite is used in collector.

Find prewittite on the map

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