Ianbruceite is a rare zinc arsenate that forms sky blue to pale blue aggregates of thin flakes and tapered platy crystals. It is a secondary mineral in the oxidized zone of a polymetallic sulfide deposit. Associated minerals include leiteite, legrandite and adamite. It was first described from the "Zinc pocket" on the 44 level, Tsumeb mine, Otjikoto (Oshikoto) region, Namibia.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareHopeite Group family

Ianbruceite

Hardness: 1
Luster: Vitreous
Streak: White
Transparency: Transparent

No image

Is this ianbruceite?

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 ianbruceite with a known reference. Ianbruceite sits at Mohs 1, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Ianbruceite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Ianbruceite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: sky blue, pale blue.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: aggregates of thin flakes and tapered platy crystals.

Often confused with

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

mineral

Hopeite

Mohs 3.5

How to tell apart: Hopeite is the harder of the two (Mohs 3.5 vs. 1).

How to tell apart: Hemimorphite is the harder of the two (Mohs 4.5-5 vs. 1).

Compare →

Often found alongside ianbruceite

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

All properties

Chemical formula: Zn₂(AsO₄)(OH)(H₂O)·2H₂O
Mohs hardness: 1
Density: 3.197 g/cm³
Colors: Sky Blue Pale Blue
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Aggregates of Thin Flakes and Tapered Platy Crystals
Cleavage: Perfect On {010}
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Polymetallic Deposits

Where rockhounds find ianbruceite

Classic worldwide localities

Tsumeb Mine, Namibia

Field-hunting tip

Look in hydrothermal polymetallic deposits country, the host setting where ianbruceite typically forms. If you start seeing tsumebite, smithsonite, cerussite in float, you are in the right ground. Field specimens usually show a aggregates of thin flakes and tapered platy crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify ianbruceite?+

Mohs hardness is 1. It typically shows a vitreous luster. The streak is white. Common colors include sky blue, pale blue.

Where is ianbruceite found?+

Notable localities include Tsumeb Mine, Namibia.

Is ianbruceite safe to handle?+

It contains toxic constituents. Contains arsenic, which is toxic if ingested or inhaled as dust. Wash hands thoroughly after handling and avoid creating dust. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like ianbruceite?+

Ianbruceite is most often confused with Hopeite, Hemimorphite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with ianbruceite?+

Ianbruceite commonly co-occurs with Tsumebite, Smithsonite, Cerussite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does ianbruceite form in?+

Ianbruceite typically forms in hydrothermal polymetallic deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is ianbruceite used for?+

Ianbruceite is used in collector.

Find ianbruceite on the map

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