boracite
noun
bo·ra·cite
ˈbōrəˌsīt,
ˈbȯr-
plural -s
: a mineral Mg3B7O13Cl consisting of a borate and chloride of magnesium that is strongly pyroelectric and occurs in hard glassy crystals and in softer white masses (hardness 7, specific gravity 2.9)
Word History
Etymology
German borazit, from Medieval Latin borac-, borax + German -it -ite