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Barrotite is a rare copper aluminum arsenate, typically intense blue. It is a secondary mineral in sandstone. Associated minerals include chalcophyllite, malachite and cuprite. It was first described from the copper mines of Roua, Alpes-Maritimes, France.

Hardness
2
Mohs
Luster
Vitreous to subadamantine
Streak
Pale blue
Transparency
Transparent to translucent

Is this barrotite?

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 barrotite with a known reference. Barrotite 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. Streak: pale blue.
  • 3
    Read the luster
    Hold the specimen under a strong light. Luster: vitreous to subadamantine.
  • 4
    Match the color range
    Compare against the expected color range: intense blue.
  • 5
    Look at form & habit
    Crystal system: trigonal. Typical habit: acicular crystals, radiating clusters.

Often confused with

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

Hemimorphite mineral
mineral
Hemimorphite
Mohs 4.5-5

How to tell apart: Hemimorphite is the harder of the two (Mohs 4.5-5 vs. 2); streak differs, so Barrotite leaves pale blue, Hemimorphite leaves white.

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Often found alongside barrotite

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

All properties

Chemical formula
Cu₉Al(HSiO₄)₂[(SO₄)(HAsO₄)₀.₅](OH)₁₂·8H₂O
Mohs hardness
2
Density
2.90 g/cm³
Colors
Intense blue
Streak
Pale blue
Luster
Vitreous to subadamantine
Transparency
Transparent to translucent
Crystal system
Trigonal
Crystal habit
Acicular crystals, radiating clusters
Cleavage
Perfect mica-like on {001}
Rarity
Rare
Uses
Collector
Host rock
Secondary in sandstone

Where rockhounds find barrotite

Classic worldwide localities

  • Barrois, France

Field-hunting tip

Where it forms: Secondary in sandstone. If you start seeing chalcophyllite, malachite, cuprite in float, you are in the right ground. Typical habit: acicular crystals, radiating clusters. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify barrotite?+
Mohs hardness is 2. Luster: vitreous to subadamantine. The streak is pale blue. Common colors include intense blue.
Where is barrotite found?+
Notable localities include Barrois, France.
Is barrotite safe to handle?+
Barrotite contains arsenic and copper and calls for real care. Contains arsenic, which is toxic if ingested or inhaled as dust. Wash hands thoroughly after handling and avoid creating dust.
What rocks look like barrotite?+
Barrotite is most often confused with Hemimorphite. A quick hardness test and a streak check separate the look-alikes faster than color alone.
What minerals are found with barrotite?+
Barrotite commonly co-occurs with Chalcophyllite, Malachite, Cuprite, Chrysocolla, Algodonite. Spotting any of these in float or country rock is a useful trip signal.
What kind of rock does barrotite form in?+
Where it forms: Secondary in sandstone. Working float back to the host body is the standard way to chase a fresh occurrence.
What is barrotite used for?+
Barrotite is used in collector.

Find barrotite on the map

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