Amygdaloid

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amygdaloid

[ə′mig·də‚lȯid]
(geology)
Lava rock containing amygdules. Also known as amygdaloidal lava.

Amygdaloid

 

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 ?
The hole drilled through uniform and amygdaloidal basalts in the footwall intersecting the mineralized zone consisting of shattered, hematized and brecciated (calcite and quartz fillings) basalts.
Basaltic fragments are abundant in the coarse lithic tuff at Gorhams Bluff where they underlie an amygdaloidal basalt flow near the top of the section.
Comprising from 10 to 20% of the rock, fragments (1-15 cm in size) include greyish pink aphyric and porphyritic felsic volcanic rocks, dark grey mudstone, greyish green amygdaloidal mafic volcanic rocks, and rare clasts of massive sulphides.
The breccia contains sparse to abundant, light grey, fine-grained, angular, amygdaloidal, porphyritic to aphyric andesite fragments from 1 to 20 cm in size set in a very fine-grained, feldspathic matrix (Fig.
These include abundant dark green, fine-grained, amygdaloidal, porphyritic basalt flows, and lesser pillow lava, basalt breccia and bedded hyaloclastite.
Amygdaloidal basalt rock units similar to those hosting lode gold deposits at the Red Lake Mines are being encountered in the current drilling program.
The Long Pond Bay Formation is defined to include a sequence of oxidized, coarsely amygdaloidal mafic volcanic flows and interbedded arkosic grit on Wood Island, and a succession of hyaloclastic mafic flows, laminated siltstone and turbiditic sandstone exposed on the southeast coast of Grand Manan Island, itself.