Wiktionary
nelenite
n. (context mineralogy English) A trigonal-hexagonal scalenohedral brown mineral containing arsenic, hydrogen, iron, magnesium, manganese, oxygen, silicon, and zinc.
Wikipedia
Nelenite
Nelenite is a rare manganese iron phyllosilicate arsenate mineral found in Franklin Furnace, New Jersey.
Its formula is (Mn,Fe)AsSiO(OH) or (Mn,Fe)(SiO)(OH)[AsO(OH)]