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A basic, dark-colored, holocrystalline, igneous rock, consisting essentially of a triclinic feldspar and pyroxene with magnetic iron; - often limited to rocks pretertiary in age. It includes part of what was early called greenstone.

A basic, dark-colored, holocrystalline, igneous rock, consisting essentially of a triclinic feldspar and pyroxene with magnetic iron; - often limited to rocks pretertiary in age. It includes part of what was early called greenstone.

d[=i]'a-b[=a]s, n. a compact igneous rock, an altered form of basalt--included under the popular names greenstone and trap.--adj. DIAB[=A]'SIC.