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Any of a group of relatively rare minerals that are chemically very similar to feldspars, but have too little silica to qualify as feldspars.
[feldspath (obsolete variant of feldspar, from obsolete German Feldspath, feldspar; see feldspar) + -oid.]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
(Geological Science) any of a group of rock-forming minerals, such as leucite and sodalite, that are similar to feldspars but contain less silica
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
feld•spath•oid(ˈfɛld spæˌθɔɪd, ˈfɛl-)
1. Also, feld`spath•oi′dal. of or pertaining to a group of minerals similar in chemical composition to certain feldspars except for a lower silica content.n.
2. a mineral of this group, as nepheline or leucite.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.