Orthogersdorffite is an orthorhombic dimorph of gersdorffite, often identified through professional mineralogical testing like X-ray diffraction. It typically appears as metallic, steel-gray masses in hydrothermal sulfide deposits alongside other nickel and arsenic minerals. Collectors should handle it with care due to its arsenic content.
Is this orthogersdorffite?
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 orthogersdorffite with a known reference. Orthogersdorffite sits at Mohs 5.5-6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: gray-black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: white, steel-gray, silver-white.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: massive, granular, or rarely as pseudocubic crystals.
Often confused with
Orthogersdorffite vs. its common look-alikes, and how to tell them apart in the field.

How to tell apart: Streak differs, so Orthogersdorffite leaves gray-black, Gersdorffite leaves grayish black.

How to tell apart: Streak differs, so Orthogersdorffite leaves gray-black, Arsenopyrite leaves black.

How to tell apart: Streak differs, so Orthogersdorffite leaves gray-black, Cobaltite leaves grayish black.
Often found alongside orthogersdorffite
Minerals reported to co-occur with orthogersdorffite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NiAsS
- Mohs hardness
- 5.5-6
- Density
- 6.0-6.4 g/cm³
- Streak
- Gray-black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Massive, granular, or rarely as pseudocubic crystals
- Cleavage
- Poor
- Rarity
- Rare
- Uses
- Collector
- Host rock
- hydrothermal veins
Where rockhounds find orthogersdorffite
Classic worldwide localities
- Gersdorff, Germany
- Schladming, Austria
- Cobalt, Canada
Field-hunting tip
Where it forms: hydrothermal veins. If you start seeing nickeline, cobaltite, quartz in float, you are in the right ground. Typical habit: massive, granular, or rarely as pseudocubic crystals. Train your eye for that shape before scanning the outcrop.



