Fernandinite is a rare calcium vanadium oxide mineral typically found as dull, fibrous crusts or earthy masses within vanadium-rich sandstone deposits. It is best identified by its distinct dark green color and its occurrence in association with secondary vanadium minerals in arid environments.
Is this fernandinite?
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 fernandinite with a known reference. Fernandinite sits at Mohs 1-2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Fernandinite leaves a light green streak.
- 3Read the lusterHold the specimen under a strong light. Fernandinite typically shows a dull luster.
- 4Match the color rangeCompare against the expected color range: dark green, blackish green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous, massive, crusts.
Often confused with
Fernandinite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Fernandinite leaves light green, Pascoite leaves yellow; luster reads dull on Fernandinite and vitreous on Pascoite.
How to tell apart: Streak differs — Fernandinite leaves light green, Hewettite leaves brownish red; luster reads dull on Fernandinite and pearly on Hewettite.
Often found alongside fernandinite
Minerals reported to co-occur with fernandinite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaV₈O₂₀·4H₂O
- Mohs hardness
- 1-2
- Density
- 2.5-3.0 g/cm³
- Colors
- Streak
- Light Green
- Luster
- Dull
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous, Massive, Crusts
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Vanadium-bearing Sandstone Deposits
- Typical price
- $20-100 for small study specimens
Where rockhounds find fernandinite
Classic worldwide localities
- Rabb Canyon, New Mexico, USA
- Colorado Plateau, USA
- Minas Ragra, Peru
Field-hunting tip
Look in vanadium-bearing sandstone deposits country — that is the host setting where fernandinite typically forms. If you start seeing gypsum, calcite, vanadinite in float, you are in the right ground. Field specimens usually show a fibrous, massive, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find fernandinite on the map
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