Duplication

There is a glitch when you place a block and then try to immediately replace it u get a real block which is placed on the ground and a fake block which when placed disappears, normally this would be fine and not a glitch, but when you use a block of diamond or something like that, which can be deconstructed in your inventory the game thinks this fake block is real and allows you to craft 9 diamonds using the fake block and leaving the real block placed on the ground resulting in duplication and no need for mining ores anymore.