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comparative more mafic, superlative most mafic
(geology) Describing rocks, such as silicate minerals, magmas, and volcanic and intrusive igneous rocks, which contain relatively high concentrations of magnesium and iron. quotations
As a whole, rocks of this type are referred to as mafic, because of the importance of magnesium and iron in their composition.
2004, Richard Fortey, The Earth, Folio Society, published 2011, page 60
plural mafics
A rock with such properties. examples