Soviet Gorshok's All Ores and Gems Map (v1.1)
All is explained within the map. It is pretty straightforward, there is pretty much every important ore and gem on this map [Pre and Post-Hardmode]. Enjoy!
Update: This map is no longer receiving any more updates on the map nor on the site. The reason is that, because development with Terraria has ended, there will never be any more additions to the ore and gem pool so there is no point to update this anymore. If you have any questions, just PM me on Steam (my username and URL is inside the map on one of the signs).