Mask it from the background, get rid of the color / color cast since black would absorb the light, then darken the shell. One curves adjustment should be all you need. Don't make it all the way black or it won't look transparent. You might need to dodge and burn to alter the way the light is reflecting because again, black absorbs light.
This is the best result i got but you can pull out the specular (highlight) details from the original photo by adding contrast using curves. duplicate the layer and desaturate it then put a multiply blending mode to it. You can then duplicate the layer again and erase the darker parts to bring out the details of the box.