ultrabasic

[ uhl-truh-bey-sik ]
/ ˌʌl trəˈbeɪ sɪk /

adjective

(of rocks) containing iron and magnesium, with little or no silica.

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Origin of ultrabasic

First recorded in 1890–95; ultra- + basic
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

Example sentences from the Web for ultrabasic

British Dictionary definitions for ultrabasic

ultrabasic
/ (ˌʌltrəˈbeɪsɪk) /

adjective

(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

Scientific definitions for ultrabasic

ultrabasic
[ ŭl′trə-bāsĭk ]

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.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.