polydymite
/pəˈlɪdɪmʌɪt/Mineralogy
noun
A mineral of the cubic system that is a sulphide of nickel, Ni3S4, occurs as grey, metallic masses of polysynthetic twin crystals, and is an endmember of a series with linnaeite.
Origin
Late 19th century. From poly- + ancient Greek -δυμ- + -ite, after German Polydymit.