Dark green crystals of the very rare mineral fernandinite associated to yellow crystals of the also rare pintadoite. Both are vanadium minerals and have only been found in a few localities worldwide. From: Slick Rock District, San Miguel County, Colorado, United States of America. — Photo: David Hospital · CC BY-SA 4.0
Fernandinite
Fernandinite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula (Ca,Na,K)₀.₉(V⁵⁺,V⁴⁺,Fe²⁺,Ti)₈O₂₀·4H₂O.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Straczekite structural group.
Key properties: specific gravity 2.78; Submetallic luster.
IMA symbol Frn, IMA status: approved, named in 1915.
Found in a rich vanadium deposit in fissures that cut red shales and that were probably filled by a remobilized asphaltite deposit.
It is found associated with Hewettite, quartz.
The name refers to Eulagio E. Fernandini, formerly an owner of the Minasragra, Peru deposit.