I have no clue whether or not this is intended, as the "Strange Sand " block (block that is smelted to make Crystal Glass) is in it's respective oredict (sand), but Crystal Glass is not in the blockGlass oredict

It does seem to be intended, as I specifically removed it in the script files. It's been over 6 months since I made the change so I can't totally remember why to be honest.. but i'm pretty sure it was due to some sort of recipe clash.