Advertisement - Continue reading below

Definition of "plagioclase" [pla•gi•o•clase]

  • Any of a common rock-forming series of triclinic feldspars, consisting of mixtures of sodium and calcium aluminum silicates. Also called oligoclase. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Use "plagioclase" in a sentence
  • "I found a moonstone (the plagioclase feldspar oligocase) almost as big as my fist, almost perfectly round."
  • "(Feldspar) plagioclase, alkali-feldspar (H 6-6. 5)"
  • "The minerals included in this group are orthoclase, microcline, and the plagioclase feldspars."