Ferroselite is a rare iron selenide mineral typically found in hydrothermal uranium-rich deposits. It is most easily identified by its distinct metallic luster and association with other selenium minerals like clausthalite, often occurring as fine-grained, radiating, or acicular crystals.
Is this ferroselite?
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 ferroselite with a known reference. Ferroselite sits at Mohs 2.5-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Ferroselite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Ferroselite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: white, gray.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular or fibrous crystals, massive aggregates, granular.
Often confused with
Ferroselite 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. 2.5-3); streak differs, so Ferroselite leaves black, Marcasite leaves greyish-black.
How to tell apart: Pyrite is the harder of the two (Mohs 6-6.5 vs. 2.5-3); streak differs, so Ferroselite leaves black, Pyrite leaves greenish-black to brownish-black.
Often found alongside ferroselite
Minerals reported to co-occur with ferroselite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- FeSe₂
- Mohs hardness
- 2.5-3
- Density
- 6.8 g/cm³
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular or Fibrous Crystals, Massive Aggregates, Granular
- Cleavage
- Distinct On {101}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins, Uranium Deposits
- Typical price
- $20-150 thumbnail
Where rockhounds find ferroselite
Classic worldwide localities
- Udykon River, Russia
- Clausthal-Zellerfeld, Germany
- Sierra de Umango, Argentina
- Temple Mountain, USA
Field-hunting tip
Look in hydrothermal veins, uranium deposits country, the host setting where ferroselite typically forms. If you start seeing clausthalite, uraninite, calcite in float, you are in the right ground. Field specimens usually show a acicular or fibrous crystals, massive aggregates, granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find ferroselite on the map
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