Kupčíkite is a very rare copper-iron-germanium sulfide that typically forms as extremely fine, black acicular or hair-like crystals. It is best identified in a laboratory setting through XRD analysis, as it is visually indistinguishable from other similar sulfosalt minerals without detailed testing.

Hardness

3-3.5

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrarenull family

Kupčíkite

Hardness: 3-3.5
Luster: Metallic
Streak: Black
Transparency: Opaque

No image

Is this kupčíkite?

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 kupčíkite with a known reference. Kupčíkite sits at Mohs 3-3.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Kupčíkite leaves a black streak.
3
Read the luster
Hold the specimen under a strong light. Kupčíkite typically shows a metallic luster.
4
Match the color range
Compare against the expected color range: black.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: acicular to hair-like crystals.

Often confused with

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

mineral

Enargite

Mohs 3

How to tell apart: Streak differs — Kupčíkite leaves black, Enargite leaves grayish-black.

Often found alongside kupčíkite

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

All properties

Chemical formula: Cu₃Fe₂GeS₆
Mohs hardness: 3-3.5
Density: 5.02 g/cm³
Colors: Black
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Orthorhombic
Crystal habit: Acicular to Hair-like Crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Vein Deposits
Typical price: $50-300 per specimen depending on size and provenance

Where rockhounds find kupčíkite

Classic worldwide localities

Cínovec, Czech Republic
Guanajuato, Mexico

Field-hunting tip

Look in hydrothermal vein deposits country — that is the host setting where kupčíkite typically forms. If you start seeing quartz, sphalerite, galena in float, you are in the right ground. Field specimens usually show a acicular to hair-like crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify kupčíkite?+

Mohs hardness is 3-3.5. It typically shows a metallic luster. The streak is black. Common colors include black.

Where is kupčíkite found?+

Notable localities include Cínovec, Czech Republic; Guanajuato, Mexico.

How much is kupčíkite worth?+

Typical asking prices fall in the range of $50-300 per specimen depending on size and provenance. Quality, size, and provenance can move individual specimens well outside that range.

Is kupčíkite safe to handle?+

It contains toxic constituents. Contains copper, iron, germanium, and sulfur; handle with care to avoid ingestion or inhalation of dust. Wash hands thoroughly after handling. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like kupčíkite?+

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

What minerals are found with kupčíkite?+

Kupčíkite commonly co-occurs with Quartz, Sphalerite, Galena, Pyrite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does kupčíkite form in?+

Kupčíkite typically forms in hydrothermal vein deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is kupčíkite used for?+

Kupčíkite is used in collector.

Find kupčíkite on the map

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