Minecraft wiki entry for Barrier, associated text: Barriers are transparent to light and do not block a beacon. Fences, iron bars, glass panes, and similar blocks do not visually connect with barriers. Barriers interact with blocks and mobs as a solid block. All dependent blocks can be placed on a barrier, such as torches or redstone, and it can suffocate mobs. Mobs cannot spawn on barriers. The red cross texture, however, is revealed as particle effects when falling or sprinting on them, regardless of what gamemode the player is in.