Pyrrhotite is a distinctive iron sulfide characterized by its bronzy, metallic luster and magnetic properties. It is often found in massive, granular forms and is a significant ore for nickel when found alongside pentlandite in magmatic sulfide deposits.
Is this pyrrhotite?
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 pyrrhotite with a known reference. Pyrrhotite sits at Mohs 3.5-4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: dark grayish black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: bronze, brown, red-brown, bronze red, dark brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: massive, platy, tabular.
Often confused with
Pyrrhotite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Pyrite is the harder of the two (Mohs 6-6.5 vs. 3.5-4.5); streak differs, so Pyrrhotite leaves dark grayish black, Pyrite leaves greenish black to brownish black.
How to tell apart: Marcasite is the harder of the two (Mohs 6-6.5 vs. 3.5-4.5); streak differs, so Pyrrhotite leaves dark grayish black, Marcasite leaves grayish or brownish black.
How to tell apart: Streak differs, so Pyrrhotite leaves dark grayish black, Pentlandite leaves pale bronze-brown.
Often found alongside pyrrhotite
Minerals reported to co-occur with pyrrhotite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe₁₋ₓS
- Mohs hardness
- 3.5-4.5
- Density
- 4.58-4.65 g/cm³
- Colors
- Streak
- Dark grayish black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Massive, platy, tabular
- Cleavage
- Parting on {0001}, distinct
- Rarity
- Common
- Uses
- Collector, Ore
- Host rock
- Mainly in mafic igneous rocks, typically as magmatic segregations; also in pegmatites, and in high-temperature hydrothermal and replacement veins, and in sedimentary and metamorphic rocks; in iron meteorites
Where rockhounds find pyrrhotite
19 mapped spotsClassic worldwide localities
- Herja (Kisbánya), Baia Mare (Nagybánya) district, Romania
- Stari Trg mine, Trepča, Serbia
- Val Passiria, Trentino-Alto Adige, and at Bottino, near Servezza, Tuscany, Italy
- Harz Mountains, at St. Andreasberg, Germany
- Bristenstock tunnel, Uri, Switzerland
- Falun, Kopparberg, Sweden
Field-hunting tip
Where it forms: Mainly in mafic igneous rocks, typically as magmatic segregations; also in pegmatites, and in high-temperature hydrothermal and replacement veins, and in sedimentary and metamorphic rocks; in iron meteorites. If you start seeing pyrite, marcasite, chalcopyrite in float, you are in the right ground. Typical habit: massive, platy, tabular. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Vermont, Idaho, Maine. Start trip planning there.
More pyrrhotite photos
Common questions
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Find pyrrhotite on the map
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