That's not the point. Identical is identical but what levels in a a rock have to be identical for you to consider it identical enough? Size, density and shape? That's only identical until you zoom to the surface and see the stuctural differences on it. Then theres the inside of the rock. Does molecular stucture need to be fully identical all the way? It's about where do you draw the line that they are identical enough. If we go all the way then I'd argue that we can erase the word identical because nothing is truly identical.