square3d.tim-daw.workers.dev… for a 3D model - also the post is updated.

"Glass develops this oily, rainbow-like iridescence through chemical corrosion by moisture. Water slowly leaches alkali ions (sodium or potassium from the flux used in making the glass) out of the surface layers. Those ions are replaced by hydrogen, leaving behind thin, hydrated, silica-rich layers. These layers can partially separate or flake, creating stacks of extremely thin films (often on the order of a micrometre or less) alternating with tiny gaps of air. Light reflecting off the multiple interfaces interferes constructively for some wavelengths and destructively for others — exactly the same optical effect that makes oil on water or a soap bubble look rainbow-coloured. The colours shift with viewing angle because the effective path length changes."