magnussonite
/ˈmaɡnəsənʌɪt/Mineralogy
noun
A green arsenite of manganese, Mn5 3+(As3+O3)3(OH,Cl), occurring as fine-grained encrustations in fissures in dolomite and haematite and crystallizing in the cubic system.
Origin
1950s. From the name of Nils H. Magnusson, former director of the Geological Survey of Sweden + -ite.