Java Edition:Redstone Ore (Item)
Redstone ore was added in Alpha v1.0.1 but the item form was not normally obtainable until Beta 1.9 Prerelease 4 with the introduction of Silk Touch. Redstone ore as an item could be obtained before being recontinued, only obtainable once in Beta 1.6 Test Build 3. This item was again discontinued for only 1 version, 12w32a, in which Silk Touch doesn't work.
Obtaining
Beta 1.6 Test Build 3 Debug Chests
In Beta 1.6 Test Build 3, any newly generated world would contain up to 11 debug chests with every item in the game. The redstone ore item was obtainable in the chests 3rd and 6th from the left in the 15th and 26th slots respectively, in stacks of 64.
Silk Touch
From Beta 1.9 Prerelease 4, Silk Touch was introduced allowing players to collect blocks in forms they previously couldn't. From this version, all a player must do is mine a redstone ore block to obtain this item. This doesn't work in 12w32a due to a bug.