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. Tennantite-(Fe) leaves a black streak.
3
Read the luster
Hold the specimen under a strong light. Tennantite-(Fe) typically shows a metallic luster.
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 — Tennantite-(Fe) leaves black, Enargite leaves grayish-black.

How to tell apart: Streak differs — Tennantite-(Fe) leaves black, Bournonite leaves steel-gray.

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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
Typical price: $20-150 for thumbnail to cabinet specimens

Where rockhounds find tennantite-(fe)

Classic worldwide localities

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

Field-hunting tip

Look in hydrothermal vein deposits country — that is the host setting where tennantite-(fe) typically forms. If you start seeing chalcopyrite, pyrite, galena in float, you are in the right ground. Field specimens usually show a tetrahedral crystals, massive, granular habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify tennantite-(fe)?+

Mohs hardness is 3-4. It typically shows a metallic luster. 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.

How much is tennantite-(fe) worth?+

Typical asking prices fall in the range of $20-150 for thumbnail to cabinet specimens. Quality, size, and provenance can move individual specimens well outside that range.

Is tennantite-(fe) safe to handle?+

It contains toxic constituents. Contains arsenic and copper. Wash hands thoroughly after handling and avoid inhaling dust or powder. Handle with care, avoid grinding or breathing dust, and store separately.

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?+

Tennantite-(Fe) typically forms in 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.