Aubertite is a rare hydrated copper aluminum sulfate chloride mineral that typically forms as a secondary product in the oxidation zones of ore deposits. Collectors primarily identify it by its distinct pale blue color and its association with other secondary sulfate minerals in arid climates.

Hardness

2-3

Mohs

Luster

Vitreous

Streak

Light blue

Transparency

Translucent

mineralrare

Aubertite

Hardness: 2-3
Luster: Vitreous
Streak: Light blue
Transparency: Translucent

Is this aubertite?

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 aubertite with a known reference. Aubertite sits at Mohs 2-3, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: light blue.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: blue, azure.
5
Look at form & habit
Crystal system: triclinic. Typical habit: tabular crystals, massive, crusts.

Often confused with

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

mineral

Chalcanthite

Mohs 2.5

How to tell apart: Streak differs, so Aubertite leaves light blue, Chalcanthite leaves white.

How to tell apart: Streak differs, so Aubertite leaves light blue, Brochantite leaves pale green.

Compare →

Often found alongside aubertite

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

All properties

Chemical formula: CuAl(SO₄)₂Cl·14H₂O
Mohs hardness: 2-3
Density: 1.815 g/cm³
Colors: Blue Azure
Streak: Light blue
Luster: Vitreous
Transparency: Translucent
Crystal system: Triclinic
Crystal habit: Tabular crystals, massive, crusts
Cleavage: {010}, perfect
Rarity: Rare
Uses: Collector
Host rock: In the oxidized zone of a copper deposit

Where rockhounds find aubertite

Classic worldwide localities

Quetena, west of Calama, Antofagasta, Chile

Field-hunting tip

Where it forms: In the oxidized zone of a copper deposit. If you start seeing copiapite, botryogen, amarantite in float, you are in the right ground. Typical habit: tabular crystals, massive, crusts. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify aubertite?+

Mohs hardness is 2-3. Luster: vitreous. The streak is light blue. Common colors include blue, azure.

Where is aubertite found?+

Notable localities include Quetena, west of Calama, Antofagasta, Chile.

Is aubertite safe to handle?+

Aubertite contains copper. Wash your hands afterwards, never grind or breathe the dust, and store it apart from specimens you handle often.

What rocks look like aubertite?+

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

What minerals are found with aubertite?+

Aubertite commonly co-occurs with Copiapite, Botryogen, Amarantite, Parabutlerite, Metahohmannite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does aubertite form in?+

Where it forms: In the oxidized zone of a copper deposit. Working float back to the host body is the standard way to chase a fresh occurrence.

What is aubertite used for?+

Aubertite is used in collector.

Find aubertite on the map

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