amygdaloid

& s. [1. Lat. amygdala; Gr. ἀμυγδάλη ( amugdale ), contracted from ἀμυγδαλέα ( amugdalea ) = the kernel of an almond. 2. Gr. εἶδος ( eidos ) = that which is seen, form, shape: εἴδω ( eido ) = to see. form of an almond.] The 11. As adj.: Almond-shaped. The more common term is AMYGDALOIDAL (Q.V.). 2. As substan. Geol. Any rock in which round or almond-shaped nodules of some mineral, such as agate, chalcedony, cale spar, or zeolite, are scattered through a base of wacke, basalt, greenstone, or other kind of trap. Amygdaloid is of volcanic origin. When bubbles of steam and gas are confined in the molten matter they form small cells. When the lava before cooling runs for some distance, the cells, originally globular, become almond shaped. The mineral which they contain is introduced, after or during consolidation, by matter separating from the ma or in filtered by water permeating the rock. (See Lyell's Manual of Geol . , ch. xxviii)