I'm certainly not the very best of the best of the best with programming, but it looks to me, according to the way you've described the problem, like somewhere down the line something stupid happened and now the game places the functional ores depending upon the metadata, but also places a bunch more and then sees the metadata for ones that shouldn't exist in the first place as something like "x/8" (You said zero through seven, which is eight integers.) where x is the actual metadata, and uses the remainder to figure out which of the possibly infinite copies of the original eight it should put and what texture it should have, like tin, diamond, coal, iron, and so on. But then, somewhere within the web of inter-mod interactions or even within the mod itself, there's a problem that makes it so that the game doesn't know if you put item y into crafting slot z, -- with y being any of the ores save for the originals and z being the top slot of a furnace -- what it is it's supposed to do, and just assumes the player is crazy and thinks this funky stuff is supposed to burn even though it, from the game's perspective, doesn't. Seems it handles names and processing into ingots differently from textures, in a way that says "If it's more than 7, it's tin, okay? Don't worry about what that weird guy who's talking about x/8 says, it's tin." Which would explain why it automatically equates any nether ore with a metadata of greater than 7 to tin, and assumes those same ores result in tin ingots. I think it could be fixed by altering config files and/or the jar itself to say "No you fool! That doesn't go there. That doesn't go ANYWHERE!" Then do a universal replace of 135:8 with nether coal, 135:9 with nether diamond, and so on in already affected areas. (Any chunks loaded into ROM before you fixed it.) If it's just one set of copies you could do it manually with server commands if you installed the right plugin, (Magic wand can do it if memory serves, but that's for Bukkit, and obviously this is Tekkit.) but if it goes up in numbers for ages, it'd probably be quicker to find out how to set something up to look for every block in pre-explored areas and replace those with the corresponding functional originals. And if all else fails and it's a big enough problem in your mind to deserve such an action, you can hit the reset button. Or a selective reset button, possibly, by completely gutting the server of the mod and deleting the nether sub-folder and any inventory instance of something that shouldn't be there any more like the inventory block versions players have already mined.