Tennantite is a copper arsenic sulfosalt that forms a solid-solution series with tetrahedrite, in which antimony takes the place of arsenic, and the two are very hard to tell apart. It is gray-black to steel-gray and metallic, forming tetrahedral crystals or granular masses in hydrothermal veins and contact metamorphic deposits with other copper, lead, zinc and silver sulfides. It is rarer than tetrahedrite. It was first described from Cornwall, England, in 1819 and named for the English chemist Smithson Tennant.

Hardness

3-4.5

Mohs

Luster

Metallic

Streak

Reddish gray

Transparency

Opaque

mineralTetrahedrite Group family

Tennantite

Also: Binnite

Hardness: 3-4.5
Luster: Metallic
Streak: Reddish gray
Transparency: Opaque

Is this tennantite?

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 tennantite with a known reference. Tennantite sits at Mohs 3-4.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: reddish gray.
3
Read the luster
Hold the specimen under a strong light. Luster: metallic.
4
Match the color range
Compare against the expected color range: flint gray, steel gray, iron black, black.
5
Look at form & habit
Crystal system: cubic. Typical habit: tetrahedral crystals; massive, granular to compact.

Often confused with

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

mineral

Tetrahedrite

Mohs 3-4.5

How to tell apart: Streak differs, so Tennantite leaves reddish gray, Tetrahedrite leaves black to brown.

Compare →

Often found alongside tennantite

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

All properties

Chemical formula: Cu₆[Cu₄(Fe,Zn)₂]As₄S₁₃
Mohs hardness: 3-4.5
Density: 4.62 g/cm³
Colors: Flint graySteel gray Iron black Black
Streak: Reddish gray
Luster: Metallic
Transparency: Opaque
Crystal system: Cubic
Crystal habit: Tetrahedral crystals; massive, granular to compact
Cleavage: None
Uses: Ore of copper
Host rock: Hydrothermal veins and contact metamorphic deposits

Where rockhounds find tennantite

Classic worldwide localities

Cornwall, England (type locality)
Tsumeb, Namibia
Butte, Montana, USA
Freiberg, Saxony, Germany
Lengenbach quarry, Binntal, Switzerland

Field-hunting tip

Where it forms: Hydrothermal veins and contact metamorphic deposits. If you start seeing pyrite, calcite, dolomite in float, you are in the right ground. Typical habit: tetrahedral crystals; massive, granular to compact. Train your eye for that shape before scanning the outcrop.

More tennantite photos

Common questions

How do you identify tennantite?+

Mohs hardness is 3-4.5. Luster: metallic. The streak is reddish gray. Common colors include flint gray, steel gray, iron black, black.

Where is tennantite found?+

Notable localities include Cornwall, England (type locality); Tsumeb, Namibia; Butte, Montana, USA; Freiberg, Saxony, Germany; Lengenbach quarry, Binntal, Switzerland.

Is tennantite safe to handle?+

Tennantite contains arsenic and copper and calls for real care. Contains arsenic and copper.

What rocks look like tennantite?+

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

What minerals are found with tennantite?+

Tennantite commonly co-occurs with Pyrite, Calcite, Dolomite, Siderite, Barite, Fluorite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does tennantite form in?+

Where it forms: Hydrothermal veins and contact metamorphic deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is tennantite used for?+

Tennantite is used in ore of copper.

Find tennantite on the map

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