from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Containing magnesium and iron and only a very small amount of silica. Used of igneous rock.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. ultramafic
from The Century Dictionary and Cyclopedia
- In petrography, extremely rich in the base-forming elements and poor in silica: applied by Judd (1881) to peridotites, hornblendites, limburgites, and related igneous rocks.
Sorry, no etymologies found.