noun
also hielm·ite ˈ(h)yelˌmīt, hēˈel-
( -s )
Etymology: Swedish hjelmit, from P. J. Hjelm died 1813 Swedish chemist + Swedish -it -ite
: a black mineral that contains yttrium, iron, manganese, uranium, calcium, columbium, tantalum, tin, and tungsten oxide, is often metamict, and has uncertain affinities — compare samarskite , tapiolite