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 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 submetallic luster.
- 4Match the color rangeCompare against the expected color range: dull 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, so Fernandinite leaves light green, Pascoite leaves yellow; luster reads submetallic on Fernandinite and vitreous on Pascoite.
How to tell apart: Streak differs, so Fernandinite leaves light 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
- 1-2
- Density
- 2.78 g/cm³
- Colors
- Streak
- Light Green
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous, Massive, Crusts
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Vanadium-bearing Sandstone Deposits
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, 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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