Kryptonite.

Kryptonite is the most famous weakness in comics. It’s the glowing remains of Superman’s home world, and it comes in far more colours than most people realise. This page covers the core five first, then every other variety, with first appearances from the sources listed below.

What is kryptonite?

Kryptonite is radioactive debris from the planet Krypton, created when the planet exploded. It travelled to Earth in meteors (in Silver Age comics, through a “space warp” from Krypton’s distant star system). Golden and Silver Age stories call it an element; after the 1986 reboot it became a compound. Lead blocks its radiation, which is why villains keep it in lead boxes.

When was kryptonite introduced?

Kryptonite was invented for radio, not the comics. It debuted in The Adventures of Superman radio serial in the episode “The Meteor from Krypton” in June 1943. A 1940 comic story called “The K-Metal from Krypton” had already used the idea, but it was never published. Kryptonite reached the comics in Superman #61 (November–December 1949), six years after its radio debut.

There’s a twist: the first kryptonite in the comics was red. DC’s own Kryptonite Catalogue (May 2025) says the rock in Superman #61 was coloured red, and that green was codified as the standard colour in Action Comics #161 (August 1951). So “1949” is right for kryptonite, and “1951” is right for green kryptonite.

The core five kryptonite colours

These are the five colours that appear most often and that every fan knows. Green and red follow DC’s Kryptonite Catalogue (2025); the others come from Wikipedia’s kryptonite table.

Green kryptonite

Green kryptonite is the classic. It causes Superman weakness and pain, strips his powers and, with long exposure, can kill him. It works on every Kryptonian, including Supergirl and the Phantom Zone criminals.

Red kryptonite

Red kryptonite causes unpredictable, temporary changes to a Kryptonian’s body or behaviour. DC lists its first appearance as Adventure Comics #255 (1958) and says its effects usually wear off after one or two days (24 or 48 hours). Earlier in 1958, World’s Finest #96 had treated red as a stronger green, ten times as radioactive. You may read that each piece only works once on a given Kryptonian: no source we trust confirms that rule, so we don’t repeat it.

Gold kryptonite

Gold kryptonite removes a Kryptonian’s powers, and in classic stories the loss is permanent. DC Guide and key-issue sites name Adventure Comics #299 (August 1962), an “imaginary story”, as its debut, with Superman #157 (November 1962) as its first appearance in continuity. Wikipedia lists Superman #178 (1965) instead.

Blue kryptonite

Blue kryptonite hurts Bizarros, the imperfect, opposite-world duplicates of Superman, and leaves Superman unharmed. It first appeared in Superman #140 (October 1960). In Smallville it removes Clark’s powers instead.

Black kryptonite

Black kryptonite splits a person into a good and an evil version. The idea came from the split-personality synthetic kryptonite in Superman III (1983) and reached the comics in Supergirl (vol. 5) #2 (October 2005).

Every other kryptonite colour

More than 20 colours have appeared. Most are one-offs, and some were jokes. This table lists the rest, with the first appearance given by Wikipedia.

Slow kryptonite, which affects humans the way green affects Kryptonians, first appeared in The Brave and the Bold #175 (1981), when Metallo modifies green kryptonite, according to DC.

Kryptonite on screen

Superman III (1983) introduced a synthetic kryptonite that splits Superman’s personality, the seed of black kryptonite. Smallville (2001–2011) used many colours with its own TV rules. In Superman (2025), Lex Luthor forces Metamorpho to turn his hand into kryptonite. See our Superman (2025) guide and the villains behind most kryptonite plots in Superman’s villains.

Is kryptonite real?

Not quite, but a real mineral came close. In 2006 mineralogist Chris Stanley at the Natural History Museum in London and colleagues confirmed a new mineral found by the mining company Rio Tinto in the Jadar Valley in Serbia. The paper came out in 2007, and in April 2007 the press noticed that its formula (sodium lithium boron silicate hydroxide) almost exactly matched the label on the kryptonite in Superman Returns (2006), which adds fluorine. It is white rather than green, doesn’t glow, contains no krypton and has no effect on anyone’s superpowers, so it was named jadarite. More British Superman connections are on Superman and Britain, and the full science story is in Real kryptonite: the science.

Is lead a weakness too?

No. Lead doesn’t hurt Superman. It blocks his X-ray vision and shields him from kryptonite radiation, which is why it turns up in so many villains’ plans. For the other things that really do hurt him, see Superman’s weaknesses.