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

3.5

Mohs

Luster

Vitreous

Streak

Light Blue

Transparency

Transparent

mineralrare

Stranskiite

Hardness: 3.5
Luster: Vitreous
Streak: Light Blue
Transparency: Transparent

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 3.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Stranskiite leaves a light blue streak.
3
Read the luster
Hold the specimen under a strong light. Stranskiite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: azure-blue, sky-blue.
5
Look at form & habit
Crystal system: triclinic. Typical habit: tabular crystals, crusts.

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 3.5 vs. 2.5); streak differs, so Stranskiite leaves light blue, Lavendulan leaves pale blue.

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: 3.5
Density: 5.38 g/cm³
Colors: Azure-blue Sky-blue
Streak: Light Blue
Luster: Vitreous
Transparency: Transparent
Crystal system: Triclinic
Crystal habit: Tabular Crystals, Crusts
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Polymetallic Ore Deposits
Typical price: $100-500 thumbnail

Where rockhounds find stranskiite

Classic worldwide localities

Tsumeb Mine, Tsumeb, Namibia

Field-hunting tip

Look in hydrothermal polymetallic ore deposits country, the host setting where stranskiite typically forms. If you start seeing tsumcorite, tennantite, adamite in float, you are in the right ground. Field specimens usually show a tabular crystals, crusts habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify stranskiite?+

Mohs hardness is 3.5. It typically shows a vitreous luster. The streak is light blue. Common colors include azure-blue, sky-blue.

Where is stranskiite found?+

Notable localities include Tsumeb Mine, Tsumeb, Namibia.

How much is stranskiite worth?+

Typical asking prices fall in the range of $100-500 thumbnail. Quality, size, and provenance can move individual specimens well outside that range.

Is stranskiite safe to handle?+

It contains toxic constituents. Contains arsenic and copper; avoid ingestion, inhalation of dust, or prolonged skin contact. Wash hands thoroughly after handling. Handle with care, avoid grinding or breathing dust, and store separately.

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 Tsumcorite, Tennantite, Adamite, Willemite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does stranskiite form in?+

Stranskiite typically forms in hydrothermal polymetallic ore deposits. 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.