Dictionary.net

• Like a peacock; resembling the tail of a peacock; iridescent. See Pavo.

1914 - Nuttall's Standard dictionary of the English language
By Nuttall, P.Austin.

• Resembling the tail of a peacock, or formed of its feathers; applied to ores and other metallic products which exhibit the brilliant hues of the peacock's tail.

1874 - Etymological and pronouncing dictionary of the English language
By Stormonth, James, Phelp, P. H.