1. ultramafic - Noun
2. ultramafic - Adjective
English Wikipedia has an article on:ultramaficWikipedia
ultramafic (comparative more ultramafic, superlative most ultramafic)
(geology) Describing igneous rocks that contain magnesium and iron and only a very small amount of silica, such as are found in the Earth’s mantle.
ultramafic (plural ultramafics)
A rock with such properties.
Hannans' tenure covers a significant strike length of the Western, Mid-Western and Takashi ultramafic belts and minor parts of the Central and Mid-Eastern ultramafic belts. Source: Internet