Essexite

Essexite ( /ˈɛsəksaɪt/), also called nepheline monzogabbro (/ˈnɛfəliːn ˌmɒnzɵˈɡæbroʊ/), is a dark gray or black holocrystalline plutonic igneous rock. Its name is derived from the type locality in Essex County, MA.