Siegenite is a member of the linnaeite group typically found as metallic, steel-gray octahedral crystals or massive granular aggregates. It is most commonly identified by its association with other base metal sulfides in hydrothermal deposits and is a notable indicator mineral for nickel-cobalt mineralization.
Is this siegenite?
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 siegenite with a known reference. Siegenite sits at Mohs 4.5-5.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: grayish black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic, brilliant on fresh surface.
- 4Match the color rangeCompare against the expected color range: steel gray, violet gray, copper red, light gray.
- 5Look at form & habitCrystal system: cubic. Typical habit: massive.
Often confused with
Siegenite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Siegenite leaves grayish black, Pentlandite leaves pale bronze-brown.
How to tell apart: Streak differs, so Siegenite leaves grayish black, Carrollite leaves black.
Often found alongside siegenite
Minerals reported to co-occur with siegenite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ni,Co)₃S₄
- Mohs hardness
- 4.5-5.5
- Density
- 4.5-4.8 g/cm³
- Colors
- Streak
- Grayish black
- Luster
- Metallic, brilliant on fresh surface
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Massive
- Cleavage
- Imperfect on {001}
- Rarity
- Uncommon
- Uses
- Collector, Ore of nickel
- Host rock
- In hydrothermal veins with other Cu–Ni–Fe sulfides
Where rockhounds find siegenite
Classic worldwide localities
- Mine la Motte, Madison Co., USA
- Buick mine, Bixby, Iron Co., and in the Miliken (Sweetwater) mine, Reynolds Co., Missouri, USA
- Siegen district, North Rhine-Westphalia (type locality), as at Müsen and Littfeld, Germany
- Brestovsko, central Bosnian Mountains, Serbia
- Kladno, Czech Republic
- Blackcraig, Kirkcudbrightshire, Scotland
Field-hunting tip
Where it forms: In hydrothermal veins with other Cu–Ni–Fe sulfides. If you start seeing chalcopyrite, pyrrhotite, galena in float, you are in the right ground. Typical habit: massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify siegenite?+
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Find siegenite on the map
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