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 — 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 — 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 — that is 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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