Phaunouxite is a rare calcium arsenate mineral that typically forms as delicate, white platy crystals or radial spray aggregates. It is found primarily in oxidized zones of arsenic-rich hydrothermal deposits and requires careful handling due to its arsenic content.

Hardness

Mohs

Luster

Pearly

Streak

White

Transparency

Translucent

mineralrareArsenate Group family

Phaunouxite

Hardness: 2
Luster: Pearly
Streak: White
Transparency: Translucent

Is this phaunouxite?

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

Often confused with

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

mineral

Pharmacolite

Mohs 2-2.5

How to tell apart: Luster reads pearly on Phaunouxite and vitreous on Pharmacolite.

How to tell apart: Luster reads pearly on Phaunouxite and vitreous on Haidingerite.

Compare →

Often found alongside phaunouxite

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

All properties

Chemical formula: Ca₃(AsO₄)₂·11H₂O
Mohs hardness: 2
Density: 2.55 g/cm³
Colors: White Colorless
Streak: White
Luster: Pearly
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Platy Crystals, Radial Aggregates
Cleavage: Perfect On {010}
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Arsenide Veins
Typical price: $50-300 per specimen

Where rockhounds find phaunouxite

Classic worldwide localities

Jachymov, Czech Republic
Bou-Azzer, Morocco

Field-hunting tip

Look in hydrothermal arsenide veins country — that is the host setting where phaunouxite typically forms. If you start seeing pharmacolite, haidingerite, arsenolite in float, you are in the right ground. Field specimens usually show a platy crystals, radial aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify phaunouxite?+

Mohs hardness is 2. It typically shows a pearly luster. The streak is white. Common colors include white, colorless.

Where is phaunouxite found?+

Notable localities include Jachymov, Czech Republic; Bou-Azzer, Morocco.

How much is phaunouxite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

Is phaunouxite safe to handle?+

It contains toxic constituents. Contains arsenic, a toxic element. Handle with care, wear gloves, wash hands after handling, and avoid inhaling dust or ingesting particles. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like phaunouxite?+

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

What minerals are found with phaunouxite?+

Phaunouxite commonly co-occurs with Pharmacolite, Haidingerite, Arsenolite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does phaunouxite form in?+

Phaunouxite typically forms in hydrothermal arsenide veins. Working float back to the host body is the standard way to chase a fresh occurrence.

What is phaunouxite used for?+

Phaunouxite is used in collector.

Find phaunouxite on the map

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