Evdokimovite is an exceptionally rare thallium-bearing sulfate mineral discovered in fumarole deposits of the Mutnovsky Volcano. It typically forms as small, colorless crystalline crusts or aggregates, often associated with other rare volcanic sulfates. Due to its thallium content and exclusive occurrence in remote volcanic vents, it is highly sought after by specialized mineral collectors.

Hardness

~2.5

Mohs

Luster

Adamantine

Streak

White

Transparency

Transparent

mineralrare

Evdokimovite

Hardness: ~2.5
Luster: Adamantine
Streak: White
Transparency: Transparent

No image

Is this evdokimovite?

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 evdokimovite with a known reference. Evdokimovite sits at Mohs ~2.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: adamantine.
4
Match the color range
Compare against the expected color range: colorless.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular crystals, crusts, aggregates.

Often confused with

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

mineral

Jarosite

Mohs 2.5-3.5

How to tell apart: Streak differs, so Evdokimovite leaves white, Jarosite leaves pale yellow; luster reads adamantine on Evdokimovite and subadamantine to vitreous, resinous on fractures on Jarosite.

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Often found alongside evdokimovite

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

All properties

Chemical formula: Tl₄(VO)₃(SO₄)₅·5H₂O
Mohs hardness: ~2.5
Density: 4.20 g/cm³
Colors: Colorless
Streak: White
Luster: Adamantine
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Tabular crystals, crusts, aggregates
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: A sublimate around a fumarole

Where rockhounds find evdokimovite

Classic worldwide localities

First scoria cone, North Breach of the Great Fissure Tolbachik volcano, Kamchatka Peninsula, Russia

Field-hunting tip

Where it forms: A sublimate around a fumarole. If you start seeing markhininite, karpovite, pauflerite in float, you are in the right ground. Typical habit: tabular crystals, crusts, aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify evdokimovite?+

Mohs hardness is ~2.5. Luster: adamantine. The streak is white. Common colors include colorless.

Where is evdokimovite found?+

Notable localities include First scoria cone, North Breach of the Great Fissure Tolbachik volcano, Kamchatka Peninsula, Russia.

Is evdokimovite safe to handle?+

Evdokimovite contains thallium and vanadium and calls for real care. Contains thallium, which is highly toxic. Handle with extreme care, avoid inhalation of dust, and wash hands thoroughly after contact.

What rocks look like evdokimovite?+

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

What minerals are found with evdokimovite?+

Evdokimovite commonly co-occurs with Markhininite, Karpovite, Pauflerite, Bobjonesite, Shcherbinaite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does evdokimovite form in?+

Where it forms: A sublimate around a fumarole. Working float back to the host body is the standard way to chase a fresh occurrence.

What is evdokimovite used for?+

Evdokimovite is used in collector.

Find evdokimovite on the map

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