plumositeMin.|ˈpluːməsaɪt| [ad.Ger.plumosit, named by Haidinger 1845, f. L. plūmōsus downy + -it, -ite1, after the older Ger. name federerz ‘feather-ore’.] = jamesonite. 1864in Webster.1881Academy 7 May 341 The recent discovery of plumosite which is a double sulphide of lead and antimony.