I'm not really sure what gives them the shine and if it is dominant or recessive. I do know that they have the grease quill gene (not sure how it is inherited. I'm guessing recessive?). It makes some quills on the sides of the bird under the wing kind of yellowy and never opens up to the down they are supposed to be. Instead, they secrete oil which makes the feathers more shiny when preening.

 

The only reference to the cause of the iridescence of Archangels I could find was on Axel Sell's website. He has the symbol Ir for the trait, and calls it an intermediate (or incomplete) dominant.

I've not been able to prove otherwise through crosses I have made or seen. Some F1's show a lot of iridescence, others normal. I am not sure either.

 

In the book GENETICS OF PIGEONS by L.P.Gibson on pages 49 and 50. This is what he has to say "The gene for Iridescence (ir) symbolized by Gibson(1993) is technically not a color gene but is a structural feather gene that produces a color effect.The effect is not one of pigmentation but rather the twisting of barbules of the feather so that they separate the light spectrum and causes a sheen to be produced.The darker the feather the more sheen is produced. The iridescence discussed here is not the tyical sheen seen on the neck of the wild type bird but rather one that affects the entire plumage such as seen in Archangels,Saxon Whitetail Firebacks, etc.The iridescence is affected by the base color and several other modifiers which includes grease quills.On a black background it appears as a beetle green,blue or purple sheen and its intensity is affected by the light source. On brown,it is not as brilliant and hardly shows at all on ash reds. It is quite striking on Bronze where the sheen is usually pinkish or purple but may be green.On recessive red, the sheen may be green or purple as on black." end of quote. GEORGE