the Lycurgus Cup
The glass contains nanoparticles that change the color of the glass based on how the light falls on them,
Stained glass is produced using gold nanoparticles based on the size of the nanoparticles.
The dark areas could be produced by dark mode SPP bose condinsate solitons. Energy enters but nothing comes out except muons. That is energy to mass conversion as seen by Holmlid.
If the surface that the analysis is looking at has been nanostructured it will be difficult to get valid data from SEM about the type of elements that the surface is made of.