You can see the difference easier in the two charms that were cast with the pearl iridescent papers and the black opaque resin layer behind. The crinkled paper charm is at the top and looks more like a real opal.
Plastic resin molds and silicone resin molds - what's the difference
Knead-a-Mold, from Townsend Atelier for DIY silicone rubber molds that set in less than 10 minutes. The final mold can be used in the oven (for polymer clay) and is food safe as well! Use to make soap?