Bonattite is a rare copper sulfate mineral that typically forms as an efflorescence in the oxidized zones of copper mines. It is characterized by its pale blue to white fibrous or crust-like habits and is usually found alongside other secondary copper minerals like chalcanthite.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrareCopiapite Group family

Bonattite

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

Is this bonattite?

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 bonattite with a known reference. Bonattite 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. Bonattite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Bonattite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: white, blue, pale blue.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: fibrous, crystalline crusts, efflorescent aggregates.

Often confused with

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

How to tell apart: Brochantite is the harder of the two (Mohs 3.5-4 vs. 2); streak differs — Bonattite leaves white, Brochantite leaves pale-green.

Often found alongside bonattite

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

All properties

Chemical formula: CuSO₄·3H₂O
Mohs hardness: 2
Density: 2.21 g/cm³
Colors: White Blue Pale Blue
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Fibrous, Crystalline Crusts, Efflorescent Aggregates
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Oxidized Zones of Copper-bearing Sulfide Deposits
Typical price: $20-100 thumbnail

Where rockhounds find bonattite

Classic worldwide localities

Tuscany, Italy
Chuquicamata, Chile
Rio Tinto, Spain

Field-hunting tip

Look in oxidized zones of copper-bearing sulfide deposits country — that is the host setting where bonattite typically forms. If you start seeing chalcanthite, gypsum, jarosite in float, you are in the right ground. Field specimens usually show a fibrous, crystalline crusts, efflorescent aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify bonattite?+

Mohs hardness is 2. It typically shows a vitreous luster. The streak is white. Common colors include white, blue, pale blue.

Where is bonattite found?+

Notable localities include Tuscany, Italy; Chuquicamata, Chile; Rio Tinto, Spain.

How much is bonattite worth?+

Typical asking prices fall in the range of $20-100 thumbnail. Quality, size, and provenance can move individual specimens well outside that range.

Is bonattite safe to handle?+

It contains toxic constituents. Contains copper; handle with care and wash hands thoroughly after handling as it is a soluble sulfate. Avoid ingestion and inhalation of dust. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like bonattite?+

Bonattite is most often confused with Chalcanthite, Brochantite, Epsomite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with bonattite?+

Bonattite commonly co-occurs with Chalcanthite, Gypsum, Jarosite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does bonattite form in?+

Bonattite typically forms in oxidized zones of copper-bearing sulfide deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is bonattite used for?+

Bonattite is used in collector.

Find bonattite on the map

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