Wilhelmkleinite is a rare zinc-iron arsenate mineral primarily known from the Tsumeb Mine in Namibia. It typically forms small, blackish green, short-prismatic crystals often associated with other rare secondary minerals in oxidized ore zones.

Hardness

4.5

Mohs

Luster

Dull, adamantine on fractures

Streak

Green

Transparency

Translucent

mineralrare

Wilhelmkleinite

Hardness: 4.5
Luster: Dull, adamantine on fractures
Streak: Green
Transparency: Translucent

Is this wilhelmkleinite?

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 wilhelmkleinite with a known reference. Wilhelmkleinite sits at Mohs 4.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: green.
3
Read the luster
Hold the specimen under a strong light. Luster: dull, adamantine on fractures.
4
Match the color range
Compare against the expected color range: blackish green.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: euhedral crystals.

Often confused with

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

mineral

Tsumcorite

Mohs 4.5

How to tell apart: Streak differs, so Wilhelmkleinite leaves green, Tsumcorite leaves yellow; luster reads dull, adamantine on fractures on Wilhelmkleinite and vitreous on Tsumcorite.

Compare →

Often found alongside wilhelmkleinite

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

All properties

Chemical formula: ZnFe³⁺₂(AsO₄)₂(OH)₂
Mohs hardness: 4.5
Density: 4.34-4.63 g/cm³
Colors: Blackish green
Streak: Green
Luster: Dull, adamantine on fractures
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Euhedral crystals
Cleavage: On {232}
Rarity: Rare
Uses: Collector
Host rock: Very rare from a deep oxidation zone in a dolostone-hosted hydrothermal polymetallic ore deposit

Where rockhounds find wilhelmkleinite

Classic worldwide localities

Tsumeb, Namibia

Field-hunting tip

Where it forms: Very rare from a deep oxidation zone in a dolostone-hosted hydrothermal polymetallic ore deposit. If you start seeing scorodite, gerdtremmelite, adamite in float, you are in the right ground. Typical habit: euhedral crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify wilhelmkleinite?+

Mohs hardness is 4.5. Luster: dull, adamantine on fractures. The streak is green. Common colors include blackish green.

Where is wilhelmkleinite found?+

Notable localities include Tsumeb, Namibia.

Is wilhelmkleinite safe to handle?+

Wilhelmkleinite contains arsenic and calls for real care. Contains arsenic, which is toxic if ingested or inhaled as dust. Wash hands thoroughly after handling and avoid grinding or creating mineral dust.

What rocks look like wilhelmkleinite?+

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

What minerals are found with wilhelmkleinite?+

Wilhelmkleinite commonly co-occurs with Scorodite, Gerdtremmelite, Adamite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does wilhelmkleinite form in?+

Where it forms: Very rare from a deep oxidation zone in 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 wilhelmkleinite used for?+

Wilhelmkleinite is used in collector.

Find wilhelmkleinite on the map

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