Rouaite is a very rare copper nitrate mineral typically found as small, vibrant blue tabular crystals or crusts. It is named after its type locality, the Roua copper mine in France, where it forms in oxidized zones of copper-rich ores.

Hardness

Mohs

Luster

Vitreous

Streak

Pale Blue

Transparency

Translucent

mineralrare

Rouaite

Hardness: 3
Luster: Vitreous
Streak: Pale Blue
Transparency: Translucent

Is this rouaite?

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 rouaite with a known reference. Rouaite sits at Mohs 3 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Rouaite leaves a pale blue streak.
3
Read the luster
Hold the specimen under a strong light. Rouaite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: blue, greenish-blue.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular crystals, crusts, radial aggregates.

Often confused with

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

mineral

Gerhardtite

Mohs 2

How to tell apart: Rouaite is noticeably harder (Mohs 3 vs. 2); streak differs — Rouaite leaves pale blue, Gerhardtite leaves light green.

How to tell apart: Streak differs — Rouaite leaves pale blue, Malachite leaves light green.

Often found alongside rouaite

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

All properties

Chemical formula: Cu₂(NO₃)(OH)₃
Mohs hardness: 3
Density: 3.51 g/cm³
Colors: Blue Greenish-blue
Streak: Pale Blue
Luster: Vitreous
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Tabular Crystals, Crusts, Radial Aggregates
Cleavage: Perfect On {010}
Rarity: Rare
Uses: Collector
Host rock: Copper-bearing Sedimentary Rocks
Typical price: $50-300 per specimen

Where rockhounds find rouaite

Classic worldwide localities

Roua Copper Mine, Daluis, France

Field-hunting tip

Look in copper-bearing sedimentary rocks country — that is the host setting where rouaite typically forms. If you start seeing gerhardtite, brochantite, calcite in float, you are in the right ground. Field specimens usually show a tabular crystals, crusts, radial aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify rouaite?+

Mohs hardness is 3. It typically shows a vitreous luster. The streak is pale blue. Common colors include blue, greenish-blue.

Where is rouaite found?+

Notable localities include Roua Copper Mine, Daluis, France.

How much is rouaite 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 rouaite safe to handle?+

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

What rocks look like rouaite?+

Rouaite is most often confused with Gerhardtite, Malachite, Connellite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with rouaite?+

Rouaite commonly co-occurs with Gerhardtite, Brochantite, Calcite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does rouaite form in?+

Rouaite typically forms in copper-bearing sedimentary rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is rouaite used for?+

Rouaite is used in collector.

Find rouaite on the map

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