tilasite
noun
til·as·ite
ˈtiləˌsīt
plural -s
: a mineral CaMg(AsO4)F consisting of a magnesium calcium arsenate and fluoride and occurring in violet-gray granular masses (specific gravity 3.3)
Word History
Etymology
Swedish tilasit, from Daniel Tilas †1772 Swedish mining engineer + Swedish -it -ite