- (of rocks) containing iron and magnesium, with little or no silica.
Origin of ultrabasic
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for ultrabasic
These range from acid to ultrabasic types and include granite, augite-diorite, picrite and serpentine.
- (of such igneous rocks as peridotite) containing less than 45 per cent silica
- Containing magnesium and iron and only a very small amount of silica. Used of igneous rock, and often used interchangeably with ultramafic. Peridotite is an ultrabasic rock.
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