Glowstone is a MV-tier material. It can be centrifuged in MV-tierCentrifuge into Gold Dust and Redstone. It is used to craft Portable Scanner, however, most of its usage begins at HV-tier and beyond.
At HV-tier it can be mixed with Silicon Dust and then smelted into Glowstone doped Monocrystalline Silicon Boule, which allows to create more advanced wafers. Finally, at EV-tier it is used to create NanoCPU Wafer, which is the main component of nanoprocessors and more advanced circuity in the mod.
Due to the excessive bulk of including all GregTech 5 blocks and items this navigation box only holds ~10% of all. The reader can view This and This navigation boxes to access the rest.