Fernandinite is a rare calcium sodium potassium oxide, typically dull green. It is a filled by a remobilized asphaltite deposit. It is associated with hewettite and quartz. It was first described from Minasragra, 46 km from Cerro de Pasco, Peru.
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 2-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: dark green.
- 3Read the lusterHold the specimen under a strong light. Luster: submetallic.
- 4Match the color rangeCompare against the expected color range: dark green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: foliated, massive.
Often confused with
Fernandinite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Fernandinite leaves dark green, Pascoite leaves cadmium-yellow; luster reads submetallic on Fernandinite and vitreous to subadamantine on Pascoite.
How to tell apart: Fernandinite is noticeably harder (Mohs 2-3 vs. ~1); streak differs, so Fernandinite leaves dark green, Hewettite leaves brownish red; luster reads submetallic on Fernandinite and silky to adamantine 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
- (Ca,Na,K)₀.₉(V⁵⁺,V⁴⁺,Fe²⁺,Ti)₈O₂₀·4H₂O
- Mohs hardness
- 2-3
- Density
- 2.78 g/cm³
- Colors
- Streak
- Dark green
- Luster
- Submetallic
- Transparency
- Opaque to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Foliated, massive
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a rich vanadium deposit in fissures that cut red shales and that were probably filled by a remobilized asphaltite deposit
Where rockhounds find fernandinite
Classic worldwide localities
- Monument No. 2 mine, Monument Valley, Apache Co., Arizona, USA
- Cactus Rat mine group, Yellow Cat district, 24 km southeast of Thompson, Grand Co., Utah, USA
- Spring Creek Mesa area, Uravan district, Montrose Co., Colorado, USA
- Minasragra, 46 km from Cerro de Pasco, Peru
Field-hunting tip
Where it forms: In a rich vanadium deposit in fissures that cut red shales and that were probably filled by a remobilized asphaltite deposit. If you start seeing hewettite, quartz in float, you are in the right ground. Typical habit: foliated, massive. 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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