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Lava rock containing amygdules. Also known as amygdaloidal lava.



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.

References in periodicals archive ?
Colorless, amethystine and smoky quartz, as well as chalcedony, occur commonly in the bottom half of zone 4 of the lower and middle amygdaloids.
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.
In 2005, the upper amygdaloid was unearthed when the quarrying operations reached the rear perimeter of the property.