Copper nickel sculptures are made of a mixture of copper and nickel. They are normally more expensive to buy because of the nickel content and more difficult to reproduce. They are cast in the same way bronze is cast.
The metal is taken to a much higher temperature before pouring. The non-ferrous metal does not oxidise like bronze and has a silver finish and I add a cold green or brown for presentation. I enjoy this medium particularly for sculptures of fish and underwater creatures, mounted on prism crystal blocks.