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ultramafic

[uhl-truh-maf-ik]
adjective Geology.
  1. ultrabasic.
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Origin of ultramafic

First recorded in 1940–45; ultra- + mafic
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
ultramafic in Science

ultramafic

[ŭl′trə-măf′ĭk]
  1. Containing mainly mafic minerals. Used of igneous rocks and often used interchangeably with ultrabasic. Dunite is an ultramafic rock.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.