I was able to farm in Elysea -> Heiron -> Nolantis Ruins for the Blood Ruby, Azure Sapphire, and Starry Diamond by walking in circles within the ruins. Again, sticking to the bottom of hills as the bottom of a hill tends to have multiple ore around. Drop-rate is random, however you need the ring Expert Essencetapping Ring equipped in order to get any chance to loot any of these at all.

Just like the Suffix of each states, the veins needing to be essencetapped are Ruby, Sapphire, and Diamond respectively.