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Related to dolerite: pegmatite
n. Chiefly British
A dark, fine-grained igneous rock; diabase.
[French dolérite, from Greek doleros, deceitful (from its easily being mistaken for diorite), from dolos, trick; see del- in Indo-European roots.]
dol′er·it′ic (ə-rĭt′ĭk) adj.
1. (Geological Science) a dark basic intrusive igneous rock consisting of plagioclase feldspar and a pyroxene, such as augite; often emplaced in dykes
2. (Geological Science) any dark igneous rock whose composition cannot be determined with the naked eye
[C19: from French dolérite, from Greek doleros deceitful; so called because of the difficulty of determining its composition]
any of various dark igneous rocks of basaltic composition, as diabase.
[1830–40; < French dolérite < Greek doler(ós) deceitful (derivative of dólos wile) + French -ite -ite1]
dol`er•it′ic (-ˈrɪt ɪk) adj.