Inyo County California, USA — Photo: Pacific Museum of Earth from Canada · CC BY-SA 2.0
Kornelite
Kornelite is an IMA-recognized mineral species in the sulfate class, with the chemical formula Fe³⁺₂(SO₄)₃·7H₂O.
It crystallizes in the monoclinic crystal system (space group P2_1/n).
Key properties: specific gravity 2.306; Silky if fibrous luster; optically biaxial.
IMA symbol Knl, grandfathered status — known before the IMA’s founding, named in 1888.
An uncommon secondary mineral produced through oxidation of pyrite.
It is found associated with Voltaite, coquimbite (Smolnı́k, Slovakia); coquimbite, römerite, copiapite, voltaite, rhomboclase (Copper Queen mine, Arizona, USA).
The mineral was named to honor Kornel Hlavacsek (1835–1914), Hungarian mining engineer at the pyrite mines, Banská Štavnica, Slovakia.