Gortdrumite is an exceptionally rare copper-mercury sulfide mineral first identified in the Gortdrum mine in Ireland. It is typically found as microscopic grains or small aggregates within copper sulfide ores, making it a prized discovery for systematic mineral collectors.

Hardness

3.5-4

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrare

Gortdrumite

Hardness: 3.5-4
Luster: Metallic
Streak: Black
Transparency: Opaque

Is this gortdrumite?

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 gortdrumite with a known reference. Gortdrumite sits at Mohs 3.5-4, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: 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: lead gray, black.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: anhedral grains, microscopic crystals.

Often confused with

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

How to tell apart: Streak differs, so Gortdrumite leaves black, Stannite leaves blackish.

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Often found alongside gortdrumite

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

All properties

Chemical formula: (Cu,Fe)₆Hg₂S₅
Mohs hardness: 3.5-4
Density: 6.8 g/cm³
Colors: Lead gray Black
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Orthorhombic
Crystal habit: Anhedral grains, microscopic crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Admixed with other sulfide minerals in a vein cutting dolomitized limestone; mineral associations suggest formation at less than 200°C

Where rockhounds find gortdrumite

Classic worldwide localities

Gortdrum deposit, near Tipperary, Co. Tipperary, Ireland (type locality)

Field-hunting tip

Where it forms: Admixed with other sulfide minerals in a vein cutting dolomitized limestone; mineral associations suggest formation at less than 200°C. If you start seeing chalcopyrite, bornite, chalcocite in float, you are in the right ground. Typical habit: anhedral grains, microscopic crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify gortdrumite?+

Mohs hardness is 3.5-4. Luster: metallic. The streak is black. Common colors include lead gray, black.

Where is gortdrumite found?+

Notable localities include Gortdrum deposit, near Tipperary, Co. Tipperary, Ireland (type locality).

Is gortdrumite safe to handle?+

Gortdrumite contains copper and mercury and calls for real care. Contains mercury and copper; handle with care and wash hands thoroughly after handling. Do not inhale dust.

What rocks look like gortdrumite?+

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

What minerals are found with gortdrumite?+

Gortdrumite commonly co-occurs with Chalcopyrite, Bornite, Chalcocite, Cinnabar, Ferroan dolomite, Barite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does gortdrumite form in?+

Where it forms: Admixed with other sulfide minerals in a vein cutting dolomitized limestone; mineral associations suggest formation at less than 200°C. Working float back to the host body is the standard way to chase a fresh occurrence.

What is gortdrumite used for?+

Gortdrumite is used in collector.

Find gortdrumite on the map

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