ganoin

or gan·o·ine

[ gan-oh-in ]
/ ˈgæn oʊ ɪn /

noun Ichthyology.

a hard, shiny, enamellike substance secreted by the corium, composing the outer layer of the scales of certain fishes.

Origin of ganoin

First recorded in 1855–60; gano(id) + -in2