Sofiite is an extremely rare secondary zinc selenite mineral discovered in volcanic fumaroles. It typically forms thin, transparent tabular crystals that are delicate and easily damaged, making it a highly sought-after prize for specialized mineral collectors.

Hardness

1.5-2

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Sofiite

Hardness: 1.5-2
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this sofiite?

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 sofiite with a known reference. Sofiite 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. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: yellow, colorless, pale yellow.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: tabular crystals, crusts, or radiating aggregates.

Often confused with

Sofiite 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 Sofiite leaves white, Klyuchevskite leaves pale green; luster reads vitreous on Sofiite and submetallic on Klyuchevskite.

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Often found alongside sofiite

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

All properties

Chemical formula: Zn₂SeO₃Cl₂
Mohs hardness: 1.5-2
Density: 4.56 g/cm³
Colors: Yellow Colorless Pale yellow
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Tabular crystals, crusts, or radiating aggregates
Cleavage: Perfect on {001}
Rarity: Rare
Uses: Collector
Host rock: fumarole deposits

Where rockhounds find sofiite

Classic worldwide localities

Tolbachik volcano, Kamchatka, Russia

Field-hunting tip

Where it forms: fumarole deposits. If you start seeing selenite, cotunnite, halite in float, you are in the right ground. Typical habit: tabular crystals, crusts, or radiating aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify sofiite?+

Mohs hardness is 1.5-2. Luster: vitreous. The streak is white. Common colors include yellow, colorless, pale yellow.

Where is sofiite found?+

Notable localities include Tolbachik volcano, Kamchatka, Russia.

Is sofiite safe to handle?+

Sofiite contains selenium. Contains selenium, which is toxic; wash hands thoroughly after handling and avoid inhalation of dust or ingestion.

What rocks look like sofiite?+

Sofiite 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 sofiite?+

Sofiite commonly co-occurs with selenite, cotunnite, halite, zincite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does sofiite form in?+

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

What is sofiite used for?+

Sofiite is used in collector.

Find sofiite on the map

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