This brown thing is a nether brick, an item made by smelting netherrack in a furnace. And netherrack is a rock-like block found in the Nether and in ruined portals. It can be mined only with a pickaxe and drops nothing if mined without one. Also, netherrack makes up most of the Nether's terrain, and also generates as part of ruined portals. Minecraft cursor pack with fanart Netherrack and Nether Brick game cursor.
