Gudmundite is a relatively uncommon iron antimony sulfide that typically appears as metallic, steel-gray masses. It is most easily identified in laboratory settings due to its striking resemblance to arsenopyrite, though it is often found in antimony-rich ore deposits rather than simple arsenic veins.
Is this gudmundite?
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 gudmundite with a known reference. Gudmundite sits at Mohs 6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Gudmundite leaves a dark gray to black streak.
- 3Read the lusterHold the specimen under a strong light. Gudmundite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: silver-white, steel-gray, creamy-white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: massive, granular, or rarely as distinct prismatic crystals.
Often confused with
Gudmundite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside gudmundite
Minerals reported to co-occur with gudmundite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- FeSbS
- Mohs hardness
- 6
- Density
- 6.9 g/cm³
- Streak
- Dark Gray to Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Massive, Granular, Or Rarely as Distinct Prismatic Crystals
- Cleavage
- None
- Rarity
- Uncommon
- Uses
- Collector, Scientific Research
- Host rock
- Hydrothermal Veins, Contact Metamorphic Deposits
- Typical price
- $20-100 per specimen depending on size and association
Where rockhounds find gudmundite
Classic worldwide localities
- Gudmundstorp, Sweden
- Broken Hill, Australia
- Boliden, Sweden
- Yellowknife, Canada
Field-hunting tip
Look in hydrothermal veins, contact metamorphic deposits country — that is the host setting where gudmundite typically forms. If you start seeing arsenopyrite, galena, sphalerite in float, you are in the right ground. Field specimens usually show a massive, granular, or rarely as distinct prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify gudmundite?+
Where is gudmundite found?+
How much is gudmundite worth?+
Is gudmundite safe to handle?+
What rocks look like gudmundite?+
What minerals are found with gudmundite?+
What kind of rock does gudmundite form in?+
What is gudmundite used for?+
Find gudmundite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
