As I mentioned before, an unpublished story "The K-Metal from Krypton" had a precedessor called "K-Metal" that removes Superman's powers. Kryptonite was created for the Superman radio serials to let Superman's voice actor rest. In 1949, kryptonite was incorpated into the comics. At first, kryptonite was rare. However, it became more common. At first, all kryptonite was green or (more rarely) red and had the same effect. In fact, Superman only figures out the origin of kryptonite after encountering red kryptonite. Later, the writers introduced the idea of different colors having different effects.
In John Byrne's reboot, the only kryptonite that was on Earth was green kryptonite that came in a fist-sized meteor. However, Mister Mxyzptlk and Ra's al Ghul both created artifical red kryptonite. Later, a meteor shower increased the amount of kryptonite on Earth.
In another reboot, it was common until Superman threw almost all kryptonite (save a small chunk he gave to Batman) into the sun thus destroying it. However, in the "New Krypton" storyline, villains and Sam Lane (Lois Lane's father) somehow got their hands on kryptonite.
Kryptonite has different effects depending on color.
- Green- This is the most commonly used form of kryptonite. It can kill Kryptonians exposed to it. However, if the kryptonite is removed, the Kryptonians are okay. In some version, it can cause cancer in humans.
- Red- Originally, red kryptonite had the same effects as green kryptonite. Later, it had random effects on Kryptonians. Post-Crisis, Ra's al Ghul created a version that caused Superman's powers to increase to level beyond his control.
- Gold- Pre-Crisis, gold kryptonite permanentaly removed Kryptonians' powers. Post-Crisis, the effect lasts for 15 seconds.
- Blue- This form hurts Bizarro, but help Kryptonians.
- Black- This has been shown to spilt the personaility of a Kryptonian into two beings.
- White- This kills all plant life with 25 yards regardlesss of if it is Kryptonian or not.
- Silver- This causes Kryptonians to act like hyperactive kids and see everything as chibi.
- Orange- This gives normal animals superpowers for 24 hours.
- Jewel- This enchances the pyshic powers of people in the Phantom Zone.
- Anti-Kryptonite- This has the effect of green kryptonite, but on non-Kryptonians.
- X-Kryptonite- This gives Earth-based life forms Kryptonian powers. It is the source of Streaky the Supercat's powers.
- Slow Kryptonite- This is a form of green kryptonite altered to hurt humans.
- Magno-Kryptonite- Created by the villain Nero (insert 2009 Star Trek movie joke here), it acts as a magentic to any substance from Krypton.
- Kryptonite-X / Kryptisium- This is a "purified form" of kryptonite. It causes Kryptonians to asborb solar enegry at a faster rate (which can cause their powers to go out of control).
- Pink- This causes Kryptonians to act like sterotypical gay people. No I am not making this up.
- Bizarro Red- This is basically red kryptonite for humans.
CompositionThe chemical structure of kryptonite varies based on the source material. In the Silver And Bronze Age, kryptonite is an element (element 126) that decays into iron. In Superman III, it is stated kryptonite is 27.71% xenon, 24.02% promethium, 18.06% tantalum, 15.08% plutonium, 10.62% dialium, 3.94% mercury and 0.57% of an unknown substance. Lego Batman 2 claims it is made up of Mercury, Dialum, Tantalum, Xenon and Promethium (a fictional DC Comics element completely different from the real life element of the same name.)