Kieftite is a rare cobalt antimonide mineral that forms part of the tilasite group, typically found in association with other cobalt minerals. It is identified primarily through laboratory analysis due to its visual similarity to more common metallic sulfides and arsenides.

Hardness

3.5

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrareTilasite Group family

Kieftite

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

No image

Is this kieftite?

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 kieftite with a known reference. Kieftite sits at Mohs 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. Kieftite leaves a black streak.
3
Read the luster
Hold the specimen under a strong light. Kieftite typically shows a metallic luster.
4
Match the color range
Compare against the expected color range: silver-white, gray.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: anhedral grains and aggregates.

Often confused with

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

mineral

Skutterudite

Mohs 5.5-6

How to tell apart: Skutterudite is the harder of the two (Mohs 5.5-6 vs. 3.5).

How to tell apart: Cobaltite is the harder of the two (Mohs 5.5 vs. 3.5); streak differs — Kieftite leaves black, Cobaltite leaves greyish-black.

Compare →

Often found alongside kieftite

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

All properties

Chemical formula: CoSb₃
Mohs hardness: 3.5
Density: 7.35 g/cm³
Colors: Silver-white Gray
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Monoclinic
Crystal habit: Anhedral Grains and Aggregates
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Veins
Typical price: $50-300 per specimen depending on size and quality

Where rockhounds find kieftite

Classic worldwide localities

Tunaberg, Sweden

Field-hunting tip

Look in hydrothermal veins country — that is the host setting where kieftite typically forms. If you start seeing skutterudite, cobaltite, chalcopyrite in float, you are in the right ground. Field specimens usually show a anhedral grains and aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify kieftite?+

Mohs hardness is 3.5. It typically shows a metallic luster. The streak is black. Common colors include silver-white, gray.

Where is kieftite found?+

Notable localities include Tunaberg, Sweden.

How much is kieftite worth?+

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

Is kieftite safe to handle?+

It contains toxic constituents. Contains antimony and cobalt. Wash hands thoroughly after handling and avoid inhaling dust or powder during cutting or crushing. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like kieftite?+

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

What minerals are found with kieftite?+

Kieftite commonly co-occurs with skutterudite, cobaltite, chalcopyrite, pyrite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does kieftite form in?+

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

What is kieftite used for?+

Kieftite is used in collector.

Find kieftite on the map

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