Stones

I was wondering how to determine the regionality of stones as granites, marbles and others. These kind of material chain is composed of at least 3 suppliers, begining 1st with the extraction supplier, who takes huges stones blocks in one state (most of them more than 500 miles). After the extraction, a 2nd supplier from another state buys this block and cut it in various slices (sometimes more, other not than 500 miles). And finally a 3rd supplier processes the slices to fit in our project needs (shape, size, roughness, others). This 3rd supplier is always within 500miles from the project. The question is: 1) as we buy the produtc from the 3rd supplier that is regional, I understand that the product is manufactured regionally. Do you agree that this interpretation is correct? 2) About extraction, as there are 2 other suppliers I understand that I can only consider regionality if both (extraction 1st and process 2nd) are within 500 miles. Is that correct? Thank you