Have found aluminium in cow dung, seem the cows like to chew up aluminium cans more so in certain area of WA, was common about the Duketon area or was a number of years ago. Have never found any gold but back to chooks, it is quite possible as they eat grit (small gravel} to help with the digestive process. Off course the common story is that those one spot nuggets have been shat out by emus..