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. Pyrrhotite leaves a dark grey to black streak.
- 3Read the lusterHold the specimen under a strong light. Pyrrhotite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: bronze, brown, red-brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular, prismatic crystals or massive, granular aggregates.
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 grey to 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 grey to black, Marcasite leaves greyish-black.
How to tell apart: Streak differs, so Pyrrhotite leaves dark grey to black, Pentlandite leaves light 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
- Streak
- Dark Grey to Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Tabular, Prismatic Crystals or Massive, Granular Aggregates
- Cleavage
- None
- Rarity
- Common
- Uses
- Collector, Ore
- Host rock
- Igneous and Metamorphic Rocks
- Typical price
- $5-50 for small specimens, $100+ for large cabinet pieces
Where rockhounds find pyrrhotite
19 mapped spotsClassic worldwide localities
- Sudbury, Ontario, Canada
- Dalnegorsk, Russia
- Santa Eulalia, Mexico
- Treptice, Czech Republic
Field-hunting tip
Look in igneous and metamorphic rocks country, the host setting where pyrrhotite typically forms. If you start seeing pentlandite, chalcopyrite, pyrite in float, you are in the right ground. Field specimens usually show a tabular, prismatic crystals or massive, granular aggregates habit, so 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.
Common questions
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Find pyrrhotite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
