View source for Amygdule

{{Short description|Infilled vesicle in extrusive igneous rock}}
{{For|part of the human brain|Amygdala}}
[[File:Vesicles in basaltic lava.JPG|thumb|right|Amygdules in lava from [[Kaiserstuhl (Baden-Württemberg)|Kaiserstuhl]] in Germany]]

'''Amygdules''' or '''amygdales''' ({{IPAc-en|ə|ˈ|m|ɪ|ɡ|dj|u:|l|z|,_|-|d|eɪ|l|z}}) form when the [[vesicular texture|vesicles]] (pores from gas bubbles in [[lava]]) of a [[volcanic rock]] or other [[extrusive rock|extrusive]] [[igneous rock]] are infilled with a secondary [[mineral]], such as [[calcite]], [[quartz]], [[chlorite group|chlorite]], or one of the [[zeolite]]s.<ref>{{cite book |last=Grapes |first=Rodney H. |year=2011 |title=Pyrometamorphism |url=https://archive.org/details/pyrometamorphism00grap_972 |url-access=limited |edition=2nd |location=Berlin, Germany |publisher=Springer Verlag |page=[https://archive.org/details/pyrometamorphism00grap_972/page/n126 115] |isbn=978-3-642-15587-1}}</ref> Amygdules usually form after the rock has been emplaced, and are often associated with low-temperature alteration. Amygdules may often be concentrically zoned. Rocks containing amygdules can be described as ''amygdaloidal''.

The word is derived from the Latin word ''amygdala'', meaning "almond tree", and the Greek word αμυγδαλή, meaning "almond"{{spaced en dash}}reflecting the typical shape of an infilled vesicle. ''Amygdule'' is more common in American usage, while ''amygdale'' is more common in British usage.

==See also==
*{{annotated link|Phenocryst}}
*{{annotated link|Volcanic gas}}

==References==
{{Reflist}}
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[[Category:Igneous petrology]]
[[Category:Igneous rocks]]


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