Tarkianite is an extremely rare copper-rhenium sulfide mineral found in hydrothermal ore deposits. It typically occurs as microscopic anhedral inclusions within other sulfide minerals, making it a difficult target for field collectors and usually requiring electron microprobe analysis for positive identification.
Is this tarkianite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch tarkianite with a known reference. Tarkianite sits at Mohs 5.5-6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: cubic. Typical habit: equant grains, euhedral crystals.
Often confused with
Tarkianite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Tarkianite is noticeably harder (Mohs 5.5-6 vs. 3-4.5).
How to tell apart: Tarkianite is noticeably harder (Mohs 5.5-6 vs. 3-3.25); streak differs, so Tarkianite leaves black, Bornite leaves pale grayish black.
Often found alongside tarkianite
Minerals reported to co-occur with tarkianite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Cu,Fe)₃(Re,Mo)₄S₈
- Mohs hardness
- 5.5-6
- Density
- 7.30 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Equant grains, euhedral crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a heavy mineral concentrate derived from a serpentinized, disseminated sulfide and PGM-bearing, ultramafic intrusion
Where rockhounds find tarkianite
Classic worldwide localities
- Hitura mine, 13 km south of Nivala, west-central Finland and the Stillwater complex, Montana, USA
- Lukkulaisvaara complex, Karelia, and Monchegorsk, Kola Peninsula, Russia, Sweden
- Ekojoki, Finland, and two localities in Sweden
Field-hunting tip
Where it forms: In a heavy mineral concentrate derived from a serpentinized, disseminated sulfide and PGM-bearing, ultramafic intrusion. If you start seeing pentlandite, chromite, pyrrhotite in float, you are in the right ground. Typical habit: equant grains, euhedral crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify tarkianite?+
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Find tarkianite on the map
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