Nether Glass (No light)

 With the bug 92 fixed in the latest snapshot , we no longer have the way to look into dark room using slabs so i thinks that we could have  a block of glass made out of soulsand that cannot let light pass trough , i could be very usefull for mobs farm or for map maker and the recipe would be very simple , we just need to put one soulsand into the furnace to make the soulglass

To  compare it it would work like the dark glass from the mod extra utilities2