"Topic for discussion, class: If one has a piece of Red K - with unique properties, by definition - and breaks it in half, does it create two new effects? COROLLARY: Each piece of Red K only affects a Kryptonian once - would two broken pieces then each have an effect on a Kryptonian?"
A reader once posed those very questions in a Metropolis Mailbag column in the mid-'60's. (And please don't ask me which issue; I don't have time to-day to go through all those issues.) Mort Weisinger's response made it clear. When the green-kryptonite swarm that passed through the cosmic cloud, transforming it in to red kryptonite, the unique properties were vested into each chunk as it existed in the swarm. Any subsequent modification of a single chunk of that red k would not alter those properties.
In other words, if red-k chunk # 1,036 acquired the property of turning Superman's hair purple, and you, as a member of the notorious Superman-Haters Gang, got your hands on it, no matter if you broke it, crumbled it, diced it, sliced it, or pureed it, the discrete components would still be "chunk # 1,036" in terms of its effect on Superman. If you broke it in two and exposed the Man of Steel to one half, his hair would turn purple. But two days later, if you exposed him to the other half, as far as his Kryptonian physiology is concerned, it's still chunk # 1,036, and it has the same properties as the other half---it would turn Supergirl's hair purple, but having affected Superman once, it would have no effect the second time.