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 olive-green tabular crystals associated with other rare selenium-bearing minerals.

Hardness

2-3

Mohs

Luster

Vitreous

Streak

Brownish green

Transparency

Transparent

mineralrare

Prewittite

Hardness: 2-3
Luster: Vitreous
Streak: Brownish green
Transparency: Transparent

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. Streak: brownish green.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: olive green.
5
Look at form & habit
Crystal system: orthorhombic. 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 2.5

How to tell apart: Streak differs, so Prewittite leaves brownish green, Klyuchevskite leaves pale green; luster reads vitreous on Prewittite and submetallic 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: KPb₁.₅ZnCu₆O₂(SeO₃)₂Cl₁₀
Mohs hardness: 2-3
Density: 3.90 g/cm³
Colors: Olive green
Streak: Brownish green
Luster: Vitreous
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Tabular to blocky crystals
Cleavage: Perfect on {010} and {101}
Rarity: Rare
Uses: Collector
Host rock: Formed by sublimation around a degassing volcanic fumarole

Where rockhounds find prewittite

Classic worldwide localities

Tolbachik volcano, Kamchatka Peninsula, Russia

Field-hunting tip

Where it forms: Formed by sublimation around a degassing volcanic fumarole. If you start seeing melanothallite, chloromenite, sophiite in float, you are in the right ground. Typical habit: tabular to blocky crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify prewittite?+

Mohs hardness is 2-3. Luster: vitreous. The streak is brownish green. Common colors include olive green.

Where is prewittite found?+

Notable localities include Tolbachik volcano, Kamchatka Peninsula, Russia.

Is prewittite safe to handle?+

Prewittite contains copper, lead and selenium. Contains lead, copper, and selenium. Wash hands thoroughly after handling and avoid inhaling dust or powder.

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 Melanothallite, Chloromenite, Sophiite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does prewittite form in?+

Where it forms: Formed by sublimation around a degassing volcanic fumarole. 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.