Origin of ultrabasic

First recorded in 1890–95; ultra- + basic
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Examples from the Web for ultrabasic

Historical Examples of ultrabasic

British Dictionary definitions for ultrabasic


  1. (of such igneous rocks as peridotite) containing less than 45 per cent silica
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

ultrabasic in Science


  1. 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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