Webster's Revised Unabridged Dictionary · 1913

Amygdaloid

Amygdaloid ({not transcribed}) , noun

[Greek {not transcribed} almond + -oid: compare French amygdaloide.]

(Mineralogy) A variety of trap or basaltic rock, containing small cavities, occupied, wholly or in part, by nodules or geodes of different minerals, esp. agates, quartz, calcite, and the zeolites. When the imbedded minerals are detached or removed by decomposition, it is porous, like lava.

Amygdaloid ({not transcribed}) , adjective

1.
Almond-shaped.
2.
Pertaining to, or having the nature of, the rock amygdaloid.

Also: Amygdaloidal