November 4, 2012

Geology Word of the Week: A is for Amygdale

Posted by Evelyn Mervine

Amygdaloidal basalt collected during dredging along the Ninetyeast Ridge in the Indian Ocean in summer 2007.

def. Amygdale (also spelled Amygule):
Vesicles, generally in extrusive igneous rocks, that are filled with secondary minerals, most commonly quartz, calcite, chlorite, and zeolite.

When a rock contains amygdales, geologists often describe it as an amygdaloidal rock. For example, basalt is often described as amygdaloidal basalt.

Here are a few previous, related geology words of the week that may be of interest:

V is for Vesicle (and Vug)

Z is for Zeolite

M is for Magma

And here are a couple more pictures of amygdaloidal rocks:

Amygdaloidal basalt from the Isle of Skye, Scotland. Picture courtesy of Matt Kuchtam.

A zeolite amygdale in a rock collected from Quartzville, Oregon. Picture courtesy of Dana Hunter.


***Thanks to my twitter follower Laura Hamilton for suggesting this week’s word. Thanks to Matt Kuchtam, Dana Hunter, and Lockwood De Witt for providing pictures.***