How do I create a new surface texture?

[jamesb33321020]

What I'm trying to do is turn a pewter pendant into jade.
I tried layering the pendant over the jade background, turning the opacity down to let the background show through, and erasing the parts I didn't want, but doesn't seem to be working nearly as well as I thought it would. 
Is there a better way?

[Ussnorway]

Is there a 3D model of this pendent and can you please share the image or the file so we can get an idea

[jamesb33321020]

[jamesb33321020]

No, I don't have a 3-d model

[Ussnorway]

well a simple option is just add a green light