Soul glass is a unique block added with nether x. It is collected by smelting soul sand in a furnace/nether furnace. It looks the same as normal glass except that it has a Brown tint to it. A really cool ability with the soul glass is that if it is hooked up to a Redstone signal, then you can walk straight through it! Don't worry about having to go to the overworld for Redstone though, because you can make buttons, pressure plates, and levers with wood and/or cobblestone, both of which can be collected in the nether. Soul glass can be crafted into any of the normal glass recipes (bottles, panes, etc.), and the soul glass panes have the same effect as the normal blocks, except that when you look through it, you cannot see very far. Another cool thing about the soul glass is that if you put a chest and/or ender chest behind it, then it will not be visible through the glass whether it is activated or not.