afaik you can add custom blocks and ores if you write them with the correct terms
what you want to do is write on block id modid:block_name
an example of this would be using the Create mod, you want to mine the Zinc ore, so what you do is put in the X-ray blockid list is create:zinc_ore
Not sure how do other mods, but an easey way to find the mod name is by using F3, you can look at the ore you want and then at the right side of the screen should be something like Targeted Block: x, y, z and right below it, will show the block name, write that specifically on the xray block list and done
(not sure if i did a good job explaining it but i hope it helps)
