ˈēstəˌnīt noun
( -s )
Usage: often capitalized
Etymology: Easton, city in eastern Pennsylvania, its locality + English -ite
: a mineral K 2 Mg 5 AlSi 5 Al 3 O 20 (OH) 4 consisting of basic silicate of potassium, aluminum, and magnesium and being an end-member of the biotite system