Texture over texture on one object on one block

I created something similar to minecraft. I generate world (x, y, z) with types of blocks (dirt, stone etc.) and create chunks (one chunk is one object with 8x32x8 "blocks" - textures of block type). But as in minecraft there is animation when you are destroying block - I mean that cracks before the block dissapear. In minecraft when you stop, cracks dissapear. But I want to let them visible (each block has HP (life) and remember it). I had an idea that I create another chunks that is similar to these chunks but only texture that has is texture with this cracks. But I think better way (less objects) is that I can normally set texture to each block how I did but I can set second texture to each block. But I dont know how to add that second texture in script and texture one has different (x, y) from texture two. Is there a way? Sorry for my bad english :D