Stranskiite is a rare secondary mineral found almost exclusively in the world-famous Tsumeb Mine in Namibia. It typically appears as striking azure-blue, thin tabular crystals or crystalline crusts associated with other rare zinc and copper arsenates.

Hardness

Mohs

Luster

Vitreous

Streak

Light blue

Transparency

Semitransparent

mineralrare

Stranskiite

Hardness: 4
Luster: Vitreous
Streak: Light blue
Transparency: Semitransparent

Is this stranskiite?

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 stranskiite with a known reference. Stranskiite sits at Mohs 4, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: light blue.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: cyanic blue.
5
Look at form & habit
Crystal system: triclinic. Typical habit: aggregates, radial.

Often confused with

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

mineral

Lavendulan

Mohs 2.5

How to tell apart: Stranskiite is noticeably harder (Mohs 4 vs. 2.5).

Compare →

Often found alongside stranskiite

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

All properties

Chemical formula: Zn₂Cu(AsO₄)₂
Mohs hardness: 4
Density: 5.23-5.3 g/cm³
Colors: Cyanic blue
Streak: Light blue
Luster: Vitreous
Transparency: Semitransparent
Crystal system: Triclinic
Crystal habit: Aggregates, radial
Cleavage: On {010}, good; on {100}, {001}, {101}, indistinct
Rarity: Rare
Uses: Collector
Host rock: A very rare secondary mineral in the oxidized zone of a dolostone-hosted hydrothermal polymetallic ore deposit

Where rockhounds find stranskiite

Classic worldwide localities

Tsumeb, Namibia

Field-hunting tip

Where it forms: A very rare secondary mineral in the oxidized zone of a dolostone-hosted hydrothermal polymetallic ore deposit. If you start seeing chalcocite, tennantite, galena in float, you are in the right ground. Typical habit: aggregates, radial. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify stranskiite?+

Mohs hardness is 4. Luster: vitreous. The streak is light blue. Common colors include cyanic blue.

Where is stranskiite found?+

Notable localities include Tsumeb, Namibia.

Is stranskiite safe to handle?+

Stranskiite contains arsenic and copper and calls for real care. Contains arsenic and copper; avoid ingestion, inhalation of dust, or prolonged skin contact. Wash hands thoroughly after handling.

What rocks look like stranskiite?+

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

What minerals are found with stranskiite?+

Stranskiite commonly co-occurs with Chalcocite, Tennantite, Galena, Schulténite, Anglesite, Bayldonite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does stranskiite form in?+

Where it forms: A very rare secondary mineral in the oxidized zone of a dolostone-hosted hydrothermal polymetallic ore deposit. Working float back to the host body is the standard way to chase a fresh occurrence.

What is stranskiite used for?+

Stranskiite is used in collector.

Find stranskiite on the map

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