Glass Shatter

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 wich 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!