Frohbergite is an uncommon iron telluride mineral typically found as microscopic inclusions within gold-telluride ores. Collectors usually seek it in polished sections or as distinct, metallic-gray aggregates associated with other telluride species in epithermal vein systems.
Is this frohbergite?
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 frohbergite with a known reference. Frohbergite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: silver white, tin white.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: granular masses, microscopic inclusions.
Often confused with
Frohbergite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Marcasite is the harder of the two (Mohs 6-6.5 vs. 3-4); streak differs, so Frohbergite leaves black, Marcasite leaves grayish or brownish black.
How to tell apart: Löllingite is the harder of the two (Mohs 5-5.5 vs. 3-4); streak differs, so Frohbergite leaves black, Löllingite leaves grayish black.
How to tell apart: Frohbergite is noticeably harder (Mohs 3-4 vs. 1.5-2); streak differs, so Frohbergite leaves black, Sylvanite leaves steel-gray to silver-white.
Often found alongside frohbergite
Minerals reported to co-occur with frohbergite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- FeTe₂
- Mohs hardness
- 3-4
- Density
- 8.055 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Granular masses, microscopic inclusions
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- In hydrothermal ore deposits, rimming chalcopyrite grains, and as inclusions in gold, petzite, or chalcopyrite
Where rockhounds find frohbergite
Classic worldwide localities
- Gold Hill, north of San Simon, Cochise Co., Arizona, USA
- Robb-Montbray (type locality) and Noranda mines, Quebec, Canada
- Lindquist Lake, British Columbia, Canada
- Bodennec, Finistère, France
- Faţa Băii (Facebánya) and Săcărı̂mb (Nagyág), Romania
- Jabal Sayid, Saudi Arabia
Field-hunting tip
Where it forms: In hydrothermal ore deposits, rimming chalcopyrite grains, and as inclusions in gold, petzite, or chalcopyrite. If you start seeing chalcopyrite, altaite, gold in float, you are in the right ground. Typical habit: granular masses, microscopic inclusions. Train your eye for that shape before scanning the outcrop.
Common questions
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Find frohbergite on the map
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