BITY's Metal Pigment Powders are great to use for all different types of props, especially weapon props.
Available in Gold, Copper and Blue Steel.

These Pigment Powders may be applied to the surface of a silicone mold. Casting resin (such as EasyFlo 60), expanding foam, or PT Flex rubber may be cast into the mold and the Metal Pigment Powder will transfer to the finished product.   

These Metal Pigment Powders are not suggested to me mixed into resins for cold casting.