Copper Firebrick Cabochon- measures 38mm x 24mm. The shadows in the pictures are from the camera lens. The cab is a uniform copper color (except for the white firebrick specks, of course).
This copper firebrick was recycled from a smelter in Michigan. It is not a natural stone. It is man-made, but unintentionally. The firebricks at the smelter became saturated with copper over the years and this is the result. This material is rare.