Instead of glass just breaking it turns in to shatters that can be build back to a block once more!
Description
When you break a glass block you get 9 Shattered Glass items (glass pane gives 6).
Then smelt them:
After you smelt them you get hot glass. With this hot glass you can make a glass pane like so:
With three hot glass you will get glass panes which you can use to craft a glass block like this:
9 glass panes will make one glass block.
Just like that you have made a glass block from Shattered Glass!