Mcbirneyite is an extremely rare copper vanadate mineral originally discovered as crusts and small platy crystals in the fumaroles of the Izalco Volcano. Collectors prize it for its vibrant deep blue color, though it is difficult to acquire due to its limited type locality and fragile nature.

Hardness

2.5-3

Mohs

Luster

Vitreous

Streak

Blue

Transparency

Translucent

mineralrare

Mcbirneyite

Hardness: 2.5-3
Luster: Vitreous
Streak: Blue
Transparency: Translucent

Is this mcbirneyite?

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 mcbirneyite with a known reference. Mcbirneyite sits at Mohs 2.5-3 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Mcbirneyite leaves a blue streak.
3
Read the luster
Hold the specimen under a strong light. Mcbirneyite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: deep blue, blue-green.
5
Look at form & habit
Crystal system: triclinic. Typical habit: platy crystals, crusts, powdery coatings.

Often confused with

Mcbirneyite 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 — Mcbirneyite leaves blue, Chalcanthite leaves white.

How to tell apart: Streak differs — Mcbirneyite leaves blue, Cuprosklodowskite leaves pale green.

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Often found alongside mcbirneyite

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

Thenardite
mineral · Mohs 2.5-3

All properties

Chemical formula: Cu₃(VO₄)₂
Mohs hardness: 2.5-3
Density: 4.49 g/cm³
Colors: Deep Blue Blue-green
Streak: Blue
Luster: Vitreous
Transparency: Translucent
Crystal system: Triclinic
Crystal habit: Platy Crystals, Crusts, Powdery Coatings
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Fumarolic Deposits
Typical price: $100-500+ for rare micro-specimens

Where rockhounds find mcbirneyite

Classic worldwide localities

Izalco Volcano, El Salvador

Field-hunting tip

Look in fumarolic deposits country — that is the host setting where mcbirneyite typically forms. If you start seeing thenardite, vanadium oxides, copper sulfates in float, you are in the right ground. Field specimens usually show a platy crystals, crusts, powdery coatings habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify mcbirneyite?+

Mohs hardness is 2.5-3. It typically shows a vitreous luster. The streak is blue. Common colors include deep blue, blue-green.

Where is mcbirneyite found?+

Notable localities include Izalco Volcano, El Salvador.

How much is mcbirneyite worth?+

Typical asking prices fall in the range of $100-500+ for rare micro-specimens. Quality, size, and provenance can move individual specimens well outside that range.

Is mcbirneyite safe to handle?+

It contains toxic constituents. Contains copper and vanadium, which are toxic if ingested or inhaled as dust. Wash hands thoroughly after handling and avoid creating dust during cleanup or specimen preparation. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like mcbirneyite?+

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

What minerals are found with mcbirneyite?+

Mcbirneyite commonly co-occurs with Thenardite, Vanadium oxides, Copper sulfates. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does mcbirneyite form in?+

Mcbirneyite typically forms in fumarolic deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is mcbirneyite used for?+

Mcbirneyite is used in collector.

Find mcbirneyite on the map

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