Keutschite is a rare mercury-bearing sulfosalt belonging to the tetrahedrite group. It typically occurs as small metallic tetrahedral crystals in hydrothermal mineral deposits and is primarily sought after by advanced systematic collectors.

Hardness

3-4

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrareTetrahedrite Group family

Keutschite

Hardness: 3-4
Luster: Metallic
Streak: Black
Transparency: Opaque

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Is this keutschite?

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 keutschite with a known reference. Keutschite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Keutschite leaves a black streak.
3
Read the luster
Hold the specimen under a strong light. Keutschite typically shows a metallic luster.
4
Match the color range
Compare against the expected color range: gray, black.
5
Look at form & habit
Crystal system: tetragonal.

Often confused with

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

How to tell apart: Streak differs, so Keutschite leaves black, Cinnabar leaves scarlet; luster reads metallic on Keutschite and adamantine on Cinnabar.

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Often found alongside keutschite

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

All properties

Chemical formula: Cu₁₂Hg₂As₄S₁₃
Mohs hardness: 3-4
Density: 4.9-5.1 g/cm³
Colors: Gray Black
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Tetragonal
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Veins

Where rockhounds find keutschite

Classic worldwide localities

Uchucchacua polymetallic deposit, Oyon district, Catajambo, Lima Department, Peru

Field-hunting tip

Look in hydrothermal veins country, the host setting where keutschite typically forms. If you start seeing cinnabar, tetrahedrite, dolomite in float, you are in the right ground.

Common questions

How do you identify keutschite?+

Mohs hardness is 3-4. It typically shows a metallic luster. The streak is black. Common colors include gray, black.

Where is keutschite found?+

Notable localities include Uchucchacua polymetallic deposit, Oyon district, Catajambo, Lima Department, Peru.

Is keutschite safe to handle?+

It contains toxic constituents. Contains mercury and arsenic; handle with care and avoid inhalation of dust or ingestion. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like keutschite?+

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

What minerals are found with keutschite?+

Keutschite commonly co-occurs with Cinnabar, Tetrahedrite, Dolomite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does keutschite form in?+

Keutschite typically forms in hydrothermal veins. Working float back to the host body is the standard way to chase a fresh occurrence.

What is keutschite used for?+

Keutschite is used in collector.

Find keutschite on the map

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