Arcubisite is an extremely rare silver-copper-bismuth sulfosalt mineral found almost exclusively in the Ilimaussaq alkaline complex of Greenland. It typically occurs as microscopic inclusions within other sulfide minerals, making it a challenging find for even advanced collectors.

Hardness

2.5

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrare

Arcubisite

Hardness: 2.5
Luster: Metallic
Streak: Black
Transparency: Opaque

Is this arcubisite?

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 arcubisite with a known reference. Arcubisite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: 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: steel gray.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: anhedral grains, microscopic crystals.

Often confused with

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

mineral

Galena

Mohs 2.5-2.75

How to tell apart: Streak differs, so Arcubisite leaves black, Galena leaves lead-gray.

How to tell apart: Streak differs, so Arcubisite leaves black, Aikinite leaves grayish black.

Compare →

Often found alongside arcubisite

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

All properties

Chemical formula: Ag₆CuBiS₄
Mohs hardness: 2.5
Density: 7.98 g/cm³
Colors: Steel gray
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Orthorhombic
Crystal habit: Anhedral grains, microscopic crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: In a cryolite deposit

Where rockhounds find arcubisite

Classic worldwide localities

Ivigtut cryolite deposit, southwestern Greenland (type locality)

Field-hunting tip

Where it forms: In a cryolite deposit. If you start seeing galena, hessite, aikinite 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 arcubisite?+

Mohs hardness is 2.5. Luster: metallic. The streak is black. Common colors include steel gray.

Where is arcubisite found?+

Notable localities include Ivigtut cryolite deposit, southwestern Greenland (type locality).

Is arcubisite safe to handle?+

Arcubisite contains copper. Contains silver, copper, and bismuth, but the primary concern is the presence of sulfur and heavy metals. Handle with care and wash hands after touching, as it may release harmful substances if powdered or heated.

What rocks look like arcubisite?+

Arcubisite is most often confused with Galena, Argentite, Aikinite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with arcubisite?+

Arcubisite commonly co-occurs with Galena, Hessite, Aikinite, Matildite, Berryite, Tellurian canfieldite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does arcubisite form in?+

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

What is arcubisite used for?+

Arcubisite is used in collector.

Find arcubisite on the map

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