Minecraft wiki entry for Redstone_circuits, associated text: Some components are not available before a player has access to the Nether, which limits the designs available. In particular, redstone comparators, observers and daylight detectors require nether quartz, which is available only from the Nether. Additionally, redstone lamps require glowstone, which is occasionally available from trading or witches, but is much more plentiful in the Nether.