Nyholmite is a rare zinc-copper arsenate mineral discovered in the Broken Hill mining district. It typically appears as small, white to colorless bladed crystals or clusters formed within the oxidized zones of ore deposits.

Hardness

3-4

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareHopeite Group family

Nyholmite

Hardness: 3-4
Luster: Vitreous
Streak: White
Transparency: Transparent

No image

Is this nyholmite?

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 nyholmite with a known reference. Nyholmite sits at Mohs 3-4 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Nyholmite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Nyholmite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: white, colorless.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: bladed crystals, aggregates.

Often confused with

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

How to tell apart: Luster reads vitreous on Nyholmite and pearly on Spencerite.

Often found alongside nyholmite

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

All properties

Chemical formula: ZnCu(AsO₄)(OH)·H₂O
Mohs hardness: 3-4
Density: 3.37 g/cm³
Colors: White Colorless
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Bladed Crystals, Aggregates
Cleavage: Perfect in One Direction
Rarity: Rare
Uses: Collector
Host rock: Oxidized Ore Zones
Typical price: $50-500 depending on specimen size and clarity

Where rockhounds find nyholmite

Classic worldwide localities

Broken Hill, New South Wales, Australia

Field-hunting tip

Look in oxidized ore zones country — that is the host setting where nyholmite typically forms. If you start seeing cuprian adamite, calcite, smithsonite in float, you are in the right ground. Field specimens usually show a bladed crystals, aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify nyholmite?+

Mohs hardness is 3-4. It typically shows a vitreous luster. The streak is white. Common colors include white, colorless.

Where is nyholmite found?+

Notable localities include Broken Hill, New South Wales, Australia.

How much is nyholmite worth?+

Typical asking prices fall in the range of $50-500 depending on specimen size and clarity. Quality, size, and provenance can move individual specimens well outside that range.

Is nyholmite safe to handle?+

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

What rocks look like nyholmite?+

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

What minerals are found with nyholmite?+

Nyholmite commonly co-occurs with Cuprian Adamite, Calcite, Smithsonite, Goethite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does nyholmite form in?+

Nyholmite typically forms in oxidized ore zones. Working float back to the host body is the standard way to chase a fresh occurrence.

What is nyholmite used for?+

Nyholmite is used in collector.

Find nyholmite on the map

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