Eclogite

Eclogite ( /ˈɛklədʒaɪt/) is a mafic (basaltic in composition) metamorphic rock; "mafic eclogite" is redundant. Eclogite is of special interest for at least two reasons. First, it forms at pressures greater than those typical of the crust of the Earth. Second, being unusually dense rock, eclogite can play an important role in driving convection within the solid Earth.