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Lava rock containing amygdules. Also known as amygdaloidal lava.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



an effusive rock with large, slightly elongated pores filled with secondary deposits of various minerals (quartz, zeolites, chlorites, and calcite). The term “amygdaloid” refers to the texture of the effusive rock regardless of its mineral composition. There are diabase, basaltic, porphyritic, and other types of amygdaloids. Amygdaloids are particularly common among ancient volcanic strata that have been subjected to hydrothermal alteration in the zeolitic facies of metamorphism.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Prehnite occurs in the amygdaloids distributed between the top of zone 4 and the upper part of zone 3.
Colorless, amethystine and smoky quartz, as well as chalcedony, occur commonly in the bottom half of zone 4 of the lower and middle amygdaloids. Crystals range in size from microscopic up to 1 cm across, normally tightly configured in pockets with only the terminations being visible.
The lower amygdaloid is about 20 meters thick--the thickest of the three layers of mineralized gas pockets.
The Fanwood quarry's middle amygdaloid is approximately 15 meters thick.