cronstedtite
noun
cron·stedt·ite
ˈkränˌstetˌīt
plural -s
: a mineral consisting of a black hydrous iron silicate of the chlorite group, crystallizing in hexagonal prisms with perfect basal cleavage, and showing a dark green streak (specific gravity 3.34–3.35)
Word History
Etymology
German cronstedit, from Baron Axel F. Cronstedt †1765 Swedish mineralogist + German -it -ite