Lead for jigs

Im new to lure making and have tied some freshwater flies. I would like to move onto saltwater bucktails and flies, and was wondering where do you get the lead used to create the jigheads? Is this a pure lead or just whatever junk you can find lying around? Do the impurities in the lead damage the melting pot at all? If i bought a pot, i would probably also use it to cast my own pistol bullets for steel target shooting

Tight Lines
Tom