Joined meshes change textures

I have created a ring with a diamond in Blender. There are two different textures; metal for the ring, glass for the diamond. When I render this everything is fine. However, when I go to animate this the meshes of move. However, when I join the meshes together, the textures darken and as a result the diamond looks almost black.

I have used YafaRay but was wondering if anybody else has had this same problem when joining meshes and rendering in Blender.

Any advice would help greatly. Thanks

I don’t think you can just join things and hope for the best. Once joined, you need to specify which faces get what texture.

Thanks for the reply. The two textures look just right