Before you push that if it hasn't occurred yet, DON'T DO THE GRAVEL THING EITHER, THAT'S CHISEL'S CONCRETE.I messed up a recipe. I meant to have it smelt gravel, it instead decided it wanted to do sand, overwriting the recipe for glass. In the minecraft/scripts/Crafting.zs, remove the line that says "furnace.addRecipe(<Silicio:materials:4>, <ore:sand>);" (line 26). Then do /mt reload, and your problem should be fixed. I'll have a version out today that fixes it, and adds Difficult Life client side, because I forgot it somehow. (still going to be disabled by default).
tl;dr: I'm an idiot