This page is about the ore. For the placeable dust, see Redstone.
Redstone is found deep underground, at about the depth that diamond can be found, however, it is much more common then diamond is. It was added in the first update of Minecraft Alpha and requires no smelting to be used. When a block of redstone is destroyed, it drops four to five piles of redstone dust.
Since it was added after the release of infdev, any save files made from before redstone was introduced will not have any in already-generated areas. Therefore, to find it, you must either start a new game, or walk a significant distance past the edge of where you have previously explored.