Tennantite-(Fe) is a common member of the tennantite group, typically characterized by its distinct tetrahedral crystal habit and steel-gray metallic luster. It is a significant copper-arsenic sulfosalt often found in hydrothermal base-metal vein systems alongside sulfides like pyrite and chalcopyrite.

Hardness

3-4

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineraluncommonTennantite Group family

Tennantite-(Fe)

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

Is this tennantite-(fe)?

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-(fe) with a known reference. Tennantite-(Fe) 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. 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, iron-black.
5
Look at form & habit
Crystal system: cubic. Typical habit: tetrahedral crystals, massive, granular.

Often confused with

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

How to tell apart: Streak differs, so Tennantite-(Fe) leaves black, Enargite leaves grayish black.

How to tell apart: Streak differs, so Tennantite-(Fe) leaves black, Bournonite leaves steel-gray to iron-black; luster reads metallic on Tennantite-(Fe) and brilliant to dull on Bournonite.

Compare →

Often found alongside tennantite-(fe)

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

All properties

Chemical formula: Cu₆(Cu₄Fe₂)As₄S₁₃
Mohs hardness: 3-4
Density: 4.6-4.7 g/cm³
Colors: Steel-gray Iron-black
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Cubic
Crystal habit: Tetrahedral crystals, massive, granular
Cleavage: None
Rarity: Uncommon
Uses: Collector, Ore of copper
Host rock: hydrothermal vein deposits

Where rockhounds find tennantite-(fe)

Classic worldwide localities

Butte, Montana, USA
Cornwall, England
Boliden, Sweden
Casapalca, Peru

Field-hunting tip

Where it forms: hydrothermal vein deposits. If you start seeing chalcopyrite, pyrite, galena in float, you are in the right ground. Typical habit: tetrahedral crystals, massive, granular. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify tennantite-(fe)?+

Mohs hardness is 3-4. Luster: metallic. The streak is black. Common colors include steel-gray, iron-black.

Where is tennantite-(fe) found?+

Notable localities include Butte, Montana, USA; Cornwall, England; Boliden, Sweden; Casapalca, Peru.

Is tennantite-(fe) safe to handle?+

Tennantite-(Fe) contains arsenic and copper and calls for real care. Contains arsenic and copper. Wash hands thoroughly after handling and avoid inhaling dust or powder.

What rocks look like tennantite-(fe)?+

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

What minerals are found with tennantite-(fe)?+

Tennantite-(Fe) commonly co-occurs with Chalcopyrite, Pyrite, Galena, Sphalerite, Siderite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does tennantite-(fe) form in?+

Where it forms: hydrothermal vein deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is tennantite-(fe) used for?+

Tennantite-(Fe) is used in collector, ore of copper.

Find tennantite-(fe) on the map

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