posnjakite
/ˈpɒznjəkʌɪt/Mineralogy
noun
A rare blue to greenish-blue mineral, occurring in encrustations and prismatic crystals, which is a hydrated basic copper sulphate, Cu4(SO4)(OH)6·H2O, closely similar to langite and crystallizing in the monoclinic system.
Origin
1960s; earliest use found in Mineralogical Abstracts. From the name of Eugene Waldemar Posnjak, U.S. geochemist + -ite, after Russian poznjakit.