Here are the gold cocoons of the Mechanitis Polymnia butterfly! According to Reddit, there are no metals in the chrysalis. It’s all organic proteins and polysaccharides, like chitin. During formation, the material forms what’s called a multilayer: a series of very thin ordered layers. The spacing between the layers (a few 10s to 100s of nanometers), and the specific properties of the materials that the layers are made of (index of refraction) determine the reflective properties of the stack (multilayer interference). Broad spectrum metallic reflection is often due to a “chirped” structure, where the layer spacing changes with stack depth. That is, the layer spacing might be thicker at the bottom and become thinner towards the top, for example. This phenomenon is called structural color!
TL;DR: Damn, that is some @sixpenceee shit!