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Also known as alkali.
Of igneous rock, containing more than average alkali (K2 O and Na2O) for that clan in which they are found.
Of igneous rock, having feldspathoids or other minerals, such as acmite, so that the molecular ratio of alkali to silica is greater than 1:6.
Of igneous rock, having a low alkali-lime index (51 or less).
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.