Isselite, sprays of acicular blue crystals. Field of view: 2 mm. Monte Ramazzo mining complex, Genoa. Photo M. Esposito. The crystal morphology is shown to the right. — Photo: M. Esposito · CC BY 4.0
Isselite
Isselite is an IMA-recognized mineral species in the sulfate class, with the chemical formula Cu₆(SO₄)(OH)₁₀(H₂O)₄·H₂O.
It crystallizes in the orthorhombic crystal system (space group Pmn2_1). It is a member of the Guarinoite structural group.
Key properties: specific gravity 3; Light blue streak; Vitreous luster; optically biaxial.
IMA symbol Iss, IMA status: approved, named in 2019.
A late-stage, secondary phase in a Fe-Ni-Co sulfide deposit.
It is found associated with Brochantite, posnjakite, pyrrhotite, pentlandite, allophane, chrysocolla, langite.
The mineral was named to honor Arturo Issel (1842-1922) for his work on the geology, paleontology, and mineralogy of Italy, especially Liguria. He was professor of Geology and Mineralogy.