Barquillite is a very rare copper mercury germanium sulfide mineral known primarily from the Bor Pit in Russia. It typically appears as dark, metallic tabular crystals or massive grains within complex sulfide-rich hydrothermal deposits.

Hardness

4-4.5

Mohs

Luster

Metallic

Streak

Gray-black

Transparency

Opaque

mineralrare

Barquillite

Hardness: 4-4.5
Luster: Metallic
Streak: Gray-black
Transparency: Opaque

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Is this barquillite?

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 barquillite with a known reference. Barquillite sits at Mohs 4-4.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: gray-black.
3
Read the luster
Hold the specimen under a strong light. Luster: metallic.
4
Match the color range
Compare against the expected color range: gray.
5
Look at form & habit
Crystal system: tetragonal. Typical habit: microscopic crystals, platy, rosette.

Often confused with

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

mineral

Germanite

Mohs 4

How to tell apart: Streak differs, so Barquillite leaves gray-black, Germanite leaves dark gray to black.

How to tell apart: Streak differs, so Barquillite leaves gray-black, Renierite leaves blackish gray.

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Often found alongside barquillite

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

All properties

Chemical formula: Cu₂CdGeS₄
Mohs hardness: 4-4.5
Density: 4.53 g/cm³
Colors: Gray
Streak: Gray-black
Luster: Metallic
Transparency: Opaque
Crystal system: Tetragonal
Crystal habit: Microscopic crystals, platy, rosette
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Very rare, in a hydrothermal Sn-Ge-Cd-Cu-Fe vein deposit

Where rockhounds find barquillite

Classic worldwide localities

Barquilla deposit, southwest Salamanca Province, Spain (type locality)

Field-hunting tip

Where it forms: Very rare, in a hydrothermal Sn-Ge-Cd-Cu-Fe vein deposit. If you start seeing tetrahedrite, greenockite, chalcopyrite in float, you are in the right ground. Typical habit: microscopic crystals, platy, rosette. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify barquillite?+

Mohs hardness is 4-4.5. Luster: metallic. The streak is gray-black. Common colors include gray.

Where is barquillite found?+

Notable localities include Barquilla deposit, southwest Salamanca Province, Spain (type locality).

Is barquillite safe to handle?+

Barquillite contains cadmium and copper and calls for real care. Contains mercury and copper; handle with care, avoid creating dust, and wash hands thoroughly after handling.

What rocks look like barquillite?+

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

What minerals are found with barquillite?+

Barquillite commonly co-occurs with Tetrahedrite, Greenockite, Chalcopyrite, Bornite, Mawsonite, Stannite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does barquillite form in?+

Where it forms: Very rare, in a hydrothermal Sn-Ge-Cd-Cu-Fe vein deposit. Working float back to the host body is the standard way to chase a fresh occurrence.

What is barquillite used for?+

Barquillite is used in collector.

Find barquillite on the map

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