A cashew shell is the same shape as the whole seed, commonly called the nut, inside. The shell has a smooth surface. The shells of ready-to-pick cashew seeds are beige in color. The shells of unripe cashew seeds are green.
Cashews are processed in a factory setting, rather than sold to consumers for shelling, because the shells contains powerful toxins similar to those found in poison ivy. The roasting process kills the toxins on cashew nuts, which makes them suitable for eating. The toxic nature of cashew shells has benefits, as the shell oil is used as an ingredient in insecticide and fungicide products.