If you buy it by the kilo, you should be able to find gem quality amethyst for under $5/gm in the rough. Look around on the net. Try rough selling groups on FB. Search with Google for gem rough dealers. If you’re asking which country has the best sellers, I don’t think there is one country, as amethyst is available from SA and Africa and a number of other places. Another thing to bear in mind is that lots of cut amethyst is synthetic and especially with ametrine, it is reputedly almost all synthetic. Learn your gemology and search for how to distinguish natural from synthetic on this site. There are telltale inclusions that indicate natural. If the stone has no inclusions, it’s impossible to tell if it’s natural or not except with tests that cost more than the stone. In the rough, you do have crystal shapes to guide you, but so much amethyst is cobbed that you may not see crystal features…is zoning only in natural, or do synthetics show it, too? I’ve forgotten, so I leave that to you. -royjohn