Pentlandite is the primary source of nickel and typically occurs in granular or massive aggregates within sulfide ore bodies. It is easily recognized by its distinct bronze-yellow color and tendency to be found in close association with magnetic pyrrhotite. Collectors often prize specimens from the major nickel-copper mining districts like Sudbury.
Is this pentlandite?
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 pentlandite with a known reference. Pentlandite sits at Mohs 3.5-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale bronze-brown.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: bronze-yellow, brownish-yellow, bronze, brown.
- 5Look at form & habitCrystal system: cubic. Typical habit: granular, massive.
Often confused with
Pentlandite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Pentlandite leaves pale bronze-brown, Pyrrhotite leaves dark grayish black.
How to tell apart: Streak differs, so Pentlandite leaves pale bronze-brown, Chalcopyrite leaves greenish black.
How to tell apart: Pyrite is the harder of the two (Mohs 6-6.5 vs. 3.5-4); streak differs, so Pentlandite leaves pale bronze-brown, Pyrite leaves greenish black to brownish black.
Often found alongside pentlandite
Minerals reported to co-occur with pentlandite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Fe,Ni)₉S₈
- Mohs hardness
- 3.5-4
- Density
- 4.6-5.0 g/cm³
- Colors
- Streak
- Pale bronze-brown
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Granular, massive
- Cleavage
- Parting on {111}
- Rarity
- Common
- Uses
- Industrial, Ore of nickel, Collector
- Host rock
- Commonly intimately associated with pyrrhotite; in ultramafic rocks and perhaps derived from them by magmatic segregation; also found in mantle xenoliths and undersea “black smoker” deposits; rarely in meteorites
Where rockhounds find pentlandite
Classic worldwide localities
- Craignure, near Inverary, Strathclyde, Scotland (type locality)
- Wheals Jane and Falmouth, Kea, Cornwall, England
- Espedalen, near Lillehammar, Opland, Norway
- Outokumpu, Vuonos, Miihkali, and Hietajärvi, in east Finland
- West Finland at the Hitura nickel deposit
- North Finland at Rarrua
Field-hunting tip
Where it forms: Commonly intimately associated with pyrrhotite; in ultramafic rocks and perhaps derived from them by magmatic segregation; also found in mantle xenoliths and undersea “black smoker” deposits; rarely in meteorites. If you start seeing pyrrhotite, troilite, chalcopyrite in float, you are in the right ground. Typical habit: granular, massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify pentlandite?+
Where is pentlandite found?+
Is pentlandite safe to handle?+
What rocks look like pentlandite?+
What minerals are found with pentlandite?+
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Find pentlandite on the map
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