Collins English-English Dictionary

dolerite ['dɒlə"raɪt]

1. 1. n a dark basic intrusive igneous rock consisting of plagioclase feldspar and a pyroxene, such as augite; often emplaced in dykes

2. 2. n any dark igneous rock whose composition cannot be determined with the naked eye

3. 3. n [Etymology] C19: from French dolérite, from Greek doleros deceitful; so called because of the difficulty of determining its composition