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This article is about the fictional element kryptonite. For other meanings, see Kryptonite (disambiguation).
Missing image
Superman, Phantom Zone criminals, and Jimmy Olsen, in front of a display of kryptonite models. From the cover of Action Comics #310, March 1964.

Kryptonite is a fictional element from the Superman comic book series. The element, usually shown as having been created from the remains of Superman's native planet of Krypton, generally has detrimental effects on Superman. The name "kryptonite" covers a variety of forms of the element, but usually refers to the most common form of kryptonite, Green Kryptonite.

Superman's first encounter with kryptonite did not take place in his comic. It was actually introduced in 1943 on the Superman radio series, as both a plot device and to allow Superman's actor, Bud Collyer, to occasionally take time off. The episode in which it first briefly appeared now exists only as a script, but the substance played a part in at least one major plotline during the course of the program. It was not until 1949 that the comic book writers incorporated it into their stories, as both a convenient danger and weakness for Superman and to add an interesting element to his stories.

Superman co-creator Jerry Siegel did write a story in 1940 that involved a piece of Krypton, referred to as "K-Metal," which robbed Superman of his strength while giving Terrans superpowers, but the story was never published.

In the traditional comics, kryptonite was believed to have originally arrived on Earth due to the experimental warp drive in the spaceship that brought Kal-El to Earth causing the ship to drag behind it all manner of debris, including a substantial amount of kryptonite. A similar explanation was also used in the television series Smallville.



Original versions

Originally, the DC Universe was home to a variety of elements collectively called kryptonite. While green was the initial and predominate version, other varieties of kryptonite began to show up with frequency beginning in the late 1950s comics, reaching a peak in appearances in 1960s Superman stories.

Kryptonite was produced from the material of Superman's home planet Krypton, when it was destroyed in an explosion. Kryptonite is usually found in the form of a glowing green rock or metal, but crystalline forms have also made appearances (most notably Jewel Kryptonite, see "Forms of Kryptonite" below) along with different-colored variants such as Red Kryptonite.

It was possible to artificially create Green Kryptonite, which the rogue genius Lex Luthor performed on various occasions.

In a 1971 storyline, all known kryptonite on Earth was transmuted into iron, but kryptonite could still be synthetically manufactured by a variety of known and unknown means, and additional material left over from the destruction of Krypton would continue to fall from space. Still, this storyline had the effect of, and achieved its purpose of, greatly reducing the use of kryptonite in Superman storylines.

Kryptonite emitted a radiation that had an adverse effect on Kryptonian natives such as Superman, though different varieties of kryptonite had different effects. It was assumed for a long time that kryptonite radiation was harmless to non-Kryptonians, but occasional isolated incidents were reported where it had sporadic effects on humans. It is not known what the half-life of any of the forms of kryptonite are.

Modern versions

After the 1985 miniseries Crisis on Infinite Earths and writer John Byrne's revision of the Superman mythos in 1986, the status of kryptonite was vastly changed. In the post-Crisis universe, only one form of Kryptonite was naturally occurring: the green variety. It was a mildly radioactive element that was formed in the crust of the planet Krypton as the result of an ancient Kryptonian war. As millennia passed, the radiation from this mineral began to kill Kryptonians; it became known as the "green plague." This eventually led to the planet's core becoming unstable, leading to the destruction of Krypton.

Two post-Crisis stories have featured artificially created Red Kryptonite. The first kind was a Kryptonite-like, but non-radioactive rock that seemingly stripped Superman of his powers (although the source was actually Mr. Mxyzptlk's magic) in the story "Krisis of the Krimson Kryptonite".

The second, in the JLA story "Tower of Babel", was created by Batman as a way of stopping Superman without killing him, should this prove necessary. It is a "relatively stable" isotope of kryptonite, which, like its pre-Crisis version, disrupts Kryptonian cells in an unpredictable way. In the story, it turned Superman's skin transparent, resulting in his "solar batteries" overloading.

In the 1990s, Jewel Kryptonite made its reappearance in modern continuity in DC's The Silver Age miniseries.

Recently in the comic Superman/Batman, a large cache of kryptonite of various hues, similar to the pre-Crisis varieties, was found on Earth, and most of it was collected and stored by the Justice League and Justice Society; what effects these varieties of kryptonite will have on future Superman stories remains uncertain.

The "science" behind kryptonite

Some issues of Superman have indicated the mechanism by which Green Kryptonite may hurt Superman. Like Hanna-Barbera's Birdman, Superman in some ways is a living solar battery; his cells absorb electromagnetic radiation from yellow stars (like Earth's sun). Kryptonite's radioactivity possibly interferes with this semi-photosynthetic process, driving the energy out of his cells in a painful fashion. Long term and high-level exposure to Green Kryptonite can be fatal to Superman. In post-Crisis comics, long-term exposure of kryptonite to human beings is known to have the same effect as exposure to Earth-borne radioactive materials; these effects include cancer. Lex Luthor discovered this inadvertently after acquiring a ring with a green Kryptonite fragment set in it to provide protection against Superman.

It is speculated that kryptonite may be located in a hypothetical "island of stability" high on the periodic table, beyond the currently known unstable elements, in the vicinity of atomic number 150. The transmutation of Earth's kryptonite could be explained by the acceleration of its natural atomic decay under this theory.

The different forms of kryptonite may represent multiple allotropes or isotopes of Green Kryptonite, or a more exotic variation in composition based on currently unknown particles.

Forms of kryptonite


The various known forms of kryptonite in the Superman comics include:

  • Green Kryptonite: In superpowered Kryptonians, causes immediate physical pain and debilitation and kills within hours. Has no short-term effects on humans (though strictly in post-Crisis continuity, long-term exposure is apparently lethal to humans) or non-superpowered Kryptonians. The most common form of kryptonite. (Note: According to DC's internal style guides of the past, "kryptonite" is capitalized only when used with a modifier ["Green Kryptonite," "Red Kryptonite," et al.].)
  • Anti-Kryptonite: Has no effect on superpowered Kryptonians, but has the same effects as Green Kryptonite on non-superpowered Kryptonians. This version of kryptonite is what killed most of the residents of Argo City in the pre-Crisis comics.
  • Red Kryptonite: Created from Green Kryptonite that passed through a mysterious red-hued cloud en route to Earth. Red Kryptonite inflicts random effects on Kryptonians, typically creating an initial "tingling effect" in those affected. Each specific chunk of Red Kryptonite has the same effect on all Kryptonians, but no two chunks have the same effect as one another. Red Kryptonite effects typically last for 24-48 hours (though sometimes as long as 72), after which the Kryptonian in question is forevermore immune to that specific chunk of Red Kryptonite. Superman has suffered the following effects upon exposure to various pieces of Red Kryptonite: being turned into a dragon, a non-powered giant, a midget, an ant-headed humanoid, a lunatic, or an amnesiac; growing an incredibly long hair and beard; being rendered totally powerless; losing his invulnerability along the left side of his body; being split into an evil Superman and a good Clark Kent; rendered unable to speak or write anything but Kryptonese, the language used on Krypton.
  • Purple Kryptonite: Gives Kryptonians mental/psychic powers, allowing them to create matter out of thin air. This effect only lasts 12-24 hours and all matter created disappears with the powers.
  • Gold Kryptonite: Removes superpowers from Kryptonians permanently, however in one story, a temporary antidote was developed that negated this effect for a short period of time. For obvious reasons, this variety was little used in Superman stories, though it played a key role in the 1986 noncanonical tale Whatever Happened to the Man of Tomorrow?
  • White Kryptonite: Kills all plant life, whether Kryptonian or not. Induces decay immediately upon exposure, with a range of about 25 yards.
  • Blue Kryptonite: The result of using Professor Potter's "duplicator ray" on some Green Kryptonite. Blue Kryptonite kills Bizarros, but has no effect on Kryptonians or humans. In the Super Friends TV series, Blue Kryptonite was once used to reverse the effects of Red Kryptonite on Superman.
  • X-Kryptonite: Created by Supergirl while experimenting with Green Kryptonite in hopes of finding an antidote. It has no effect on Kryptonians, but bestows temporary superpowers on Earth lifeforms, most prominently Supergirl's pet cat, Streaky (see: Streaky the Supercat).
  • Jewel Kryptonite: Jewel Kryptonite amplifies the psychic powers of Phantom Zone residents, allowing them to project illusions into the "real world" or perform mind control. It was made from what was left of a mountain range on Krypton called the Jewel Mountains.
  • Slow Kryptonite: A modified variety of Green Kryptonite produced by a Terran scientist that decelerates the speed of nerve impulses and movements of both Kryptonians and Terrans. Appeared in The Brave and the Bold #177.
  • Magno-Kryptonite: A piece of kryptonite that is magnetically attracted to all substances originally from Krypton, according to Superman's Pal, Jimmy Olsen #91.
  • Bizarro Red Kryptonite: Affects humans the same way Red Kryptonite affects Kryptonians. Appeared in Superman's Pal, Jimmy Olsen #80.
  • Pink Kryptonite: From an alternate timeline in a 2003 Supergirl storyline, this variety of kryptonite apparently turned heterosexual Kryptonians into homosexuals. However, this version of kryptonite has not been used in mainstream comics continuity.


In the comics, several varieties of kryptonite that turned out to be hoaxes include:

  • Silver Kryptonite: A fictional variety of kryptonite that was used in a hoax perpetrated by Superman's friends, in honor of the 25th (or "silver") anniversary of Superman's arrival on Earth.
  • Yellow Kryptonite: Another fictional variety, this one was used in a hoax masterminded by Lex Luthor.

In other media

As noted above, kryptonite was originally created for the 1940s Superman radio series. Kryptonite has appeared in various forms in the various Superman media spinoffs, however.

Most depictions of kryptonite in the various films and TV series of Superman have largely been limited to Green Kryptonite, with occasional appearances of Red Kryptonite and Blue Kryptonite.

Kryptonite was featured in Superman: The Movie. An imperfect synthesis of artificial kryptonite containing tar that turned Superman evil appeared in Superman III.

In the 1990s television series Lois and Clark: The New Adventures of Superman, a scientist created "Hybrid Kryptonite," which has no effect on Kryptonians but hurts humans. Red Kryptonite also was featured in the series. In one episode it made Superman apathetic; in another, it transferred his powers to Lois Lane.

In the television series Smallville, the show expands on the concept of the substance being harmful to humans. On the show, not only is Green Kryptonite (referred to in the series as "meteor rock") harmful to Clark Kent, but it can produce bizarre changes in humans and animals, typically turning them into powerful mutant menaces, commonly known by the denizens of Smallville as "Meteor Freaks," that Clark must oppose. These changes seem to be linked to the condition in which the subject was exposed to kryptonite. Groups of people have been shown to acquire the same powers from Kryptonite by exposing themselves to it in the same manner.

Red Kryptonite has also been shown in Smallville. Its effect on Clark Kent is to rid him of all inhibitions, making him rebellious and potentially dangerous if exposed to it for too long. Also created for the series was "Black Kryptonite" (first appearing in the episode "Crusade"), which was able to separate certain entities from people, particularly humans' good and evil sides, as Lex Luthor experienced when he was split into "good" and "evil" selves by Black Kryptonite.

Size of Krypton?

Several sources have calculated the total mass of the planet Krypton based on the estimated mass of Kryptonite that fell to Earth, based on the assumption that the initial explosive distribution of pieces of Krypton was isotropic, and determinations of the mean distance between Krypton and Earth derived from certain passages in the Essene New Testament. The results are confusing at best, as the estimated mass of Krypton is 107 times the mass of our own sun, which would imply that the creation of a black hole would be inevitable, and the existence of corporeal life on the planet beforehand being highly questionable. Most comic depictions of Krypton's destruction have shown, however, that its core was in a highly unstable state, and the key to the planet's death.

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