Kryptonite is a fictional substance from the Superman comic book series (and subsequent related media). The material, usually shown as having been created from the remains of Superman's native planet of Krypton, generally has detrimental effects on Superman and any other Kryptonian exposed to it. The name "kryptonite" covers a variety of forms of the substance, but usually refers to the most common "green" form.

Kryptonite was produced from the material of Krypton, when it was destroyed in an explosion. It 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 the red form.

Recently, a mining group in Serbia discovered a new mineral, called Jadarite, the chemical composition of which is sodium lithium boron silicate hydroxide, the chemical formula for Kryptonite written on a case of the substance in the film Superman Returns minus fluoride. The newly discovered mineral was first analyzed by Dr. Chris Stanley, a minerologist at the London Museum of Natural History. However, the 'real' Kryptonite doesn't appear to have anything in common with the film's version other than the chemical formula. The new mineral is white, or pinkish under UV light, hard in texture but chalky in appearance, and made of tiny crystals less than 5 microns in diameter. It isn't thought to possess any of Kryptonite's supernatural powers.

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History

Original versions

Originally, the DC Universe was home to a variety of minerals collectively called kryptonite. The most commonly depicted variety of kryptonite is greenish in coloring, though it was colored red in its first appearance in Superman (volume 1) #61 (November / December 1949). In Adventure Comics (volume 1) #171 (December 1950) the kryptonite shown trapping Superboy was colored purple but acted just like regular Green. Other varieties of kryptonite began to show up frequently beginning in the late 1950s comics, reaching a peak in appearances in 1960s Superman series.

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 The K-Metal from Krypton, which robbed Superman of his strength while giving humans superpowers, but the story was never published.

The amount of kryptonite shown to fall on the Earth in Silver Age stories is too large to have been evenly distributed from the explosion of any reasonably sized planet, so the usual explanation for the large amount that made it to Earth was that the kryptonite and other materials from Krypton were dragged to Earth by the experimental warp drive that brought Superman to Earth. A similar explanation has been used in many subsequent continuities, such as the 1990s television series Lois and Clark: The New Adventures of Superman, Superman: The Animated Series, the graphic novel Superman: Birthright and the 2000s television series Smallville(which saw a massive amount of the material arrive with Kal-El's ship, devastating Smallville with a violent meteorite shower).

It was possible to artificially create green kryptonite, which the rogue genius Lex Luthor performed on various occasions. However, he rarely needed to do so, as kryptonite was so abundant that many ordinary criminals kept a supply as a precaution against Superman's interference. In a 1971 storyline, all known kryptonite on Earth was transmuted into iron (and the existence of kryptonite on the moon was classified for decades), 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 achieved its intended 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.

Modern versions

After the 1985 limited series Crisis on Infinite Earths and writer John Byrne's subsequent revision of the series 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. As revealed in the World of Krypton mini-series the abortive detonation of a doomsday device by the Black Zero terrorist group set off a slow chain reaction within Krypton's core causing the native elements of Krypton to fuse together into a new radioactive element.

As millennia passed, the unique background radiation from this element began to kill increasing numbers of Kryptonians. The authorities suppressed knowledge of the "green death", but the scientist Jor-El was able to trace the source of the radiation. He discovered that the amount of the new element in Krypton's core was reaching critical mass and that it would soon explode, destroying the planet. This was a parallel to the pre-Crisis version of Krypton which was destroyed when its uranium core exploded. A non-canonical roleplaying game supplement by comic book writer Roger Stern called the new element "kryptonium" with kryptonite being its common ore. However, this has not been acknowledged within the comic books.

Initially kryptonite was much rarer on Earth in the revised stories, the only available sample being a fist-sized chunk which had embedded itself in the tail of Kal-El's rocketship as it fled from the exploding planet Krypton. It was later secretly removed from the rocketship by a government cabal to become the power source for the cyborg Metallo. That sample was also responsible for triggering the powers of the supervillain Conduit. The sample was in turn stolen by Lex Luthor who had a piece cut from the main stone and mounted in a signet ring to keep Superman at bay. However, continued exposure to the ring proved carcinogenic to Luthor (a significant difference from Silver Age stories, in which kryptonite was completely harmless to humans), necessitating the amputation of his hand and ultimately causing his supposed death. Superman recovered the ring and entrusted it to Batman to be used if he ever became a threat to humanity. During Infinite Crisis this ring was destroyed by Kal-L of Earth-2. Another part of the stone was cut into a kryptonite bullet. An unknown fraction of the first sample is securely stored in the Fortress of Solitude.

As pieces of the Lexcorp sample were distributed, many fell into the possession of other criminal organizations and supervillains. For many years the only way a character could have access to kryptonite in the DC Universe was to have a piece of this original sample, or to somehow fetch it from the remains of Krypton itself. However, this situation recently changed with the appearance of the new Supergirl in the Superman/Batman series, during which the arrival of Supergirl's spaceship was accompanied by a fall of several tons worth of kryptonite into Gotham Bay.

A variety of kryptonite types similar to the pre-Crisis range appeared in the Pocket Universe created by Legion of Super-Heroes villain the Time Trapper. Superman, while visiting the pocket universe, used this universe's native Gold Kryptonite (Superman found he was immune to the kryptonite that existed in that universe) to remove the powers of General Zod and several other Phantom Zone criminals who had destroyed all life on that world; Superman then executed the criminals by use of green kryptonite, as punishment for the villains' crime.

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 Justice League story "Tower of Babel", was created by Batman as a way of stopping Superman without killing him, should this prove necessary. It was stolen by Ra's al Ghul, who quickly put it to use. 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 limited series.

Later, 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.

As shown in the Action Comics Annual #10, Lex Luthor put a piece of red, green, gold, and blue kryptonite into Metallo.

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 stars (like Earth's sun). Kryptonite's radioactivity possibly interferes with this 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 to kryptonite is known to have the same effects on human beings as exposure to Earth-born 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—Luthor first lost the hand he wore the ring on to cancer and later had to have his brain transferred into a new, cloned body after the cancer was found to have spread throughout his original body.

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.

Under normal chemical nomenclature the -ite suffix would denote a compound (e.g. the compound uranite contains the element uranium). Thus the name implies that kryptonite is a compound and not an element (something supported by the "tar" analysis in the third Superman movie). This issue was normally overlooked in the pre Crisis comic books, but a non-canonical game sourcebook did refer to kryptonite as "the common ore of the super-actinide Kryptonium, an unusually stable transuranic element, whose atomic number is believed to be 126." The half-life of kryptonium is listed as 250,000 years. (Stern, Roger (1992) Superman: The Man of Steel Sourcebook Mayfair Games)

One thought about the source of the -ite ending is found in astronomy wherein a meteoroid is a rock floating in deep space, a meteor is one streaking through the sky, and a meteorite is a rock lying around on the ground after falling from the sky. The -ite ending could have been used to denote chunks of Krypton that had fallen to Earth.

The aforementioned atomic number was reinforced by the first season episode of Lois and Clark: The New Adventures of Superman entitled "The Green, Green Glow of Home," where it was stated that kryptonite was "periodic element 126" and that it "emits an extremely high band radiation that does not seem to affect humans". The substance itself had no formal designation until the very end of the episode, where Lois Lane's suggestion that it be named "kryptonium" was eschewed in favor of Clark Kent's "kryptonite" due to the fact that it initially appeared in the form of a meteorite.

The atomic number 126 is the one of the hypothesized unbihexium/eka-plutonium, the most stable of the elements in the island of stability.

Action Comics #591 would formally have Kryptonite as a compound in the Post-Crisis DCU.

In Superman Returns, an additional piece of kryptonite is found in a rock fragment, once more in Addis Ababa. Lex Luthor steals it from a Metropolis museum and uses it in his quest to create a new kryptonite landmass. During the extraction process, the rock appears to hold a significant amount of green kryptonite. The scientific name for the rock was displayed on its case, 'Sodium lithium boron silicate hydroxide with fluorine'. As borosilicate glass is commonly crystalline and green-tinted, this could be a plausible human mis-identification of kryptonite; alternately, as no 'unknown' component is listed, one might assume this (sodium/lithium/borosilicate/fluorine) blend to be the actual composition of green kryptonite. Though more likely, the researchers who performed the analysis of the fragment did not perform a core sample test. They may have only chipped off the outer layer in order to test it.

Amazingly, in April 2007 it was announced that geologists in Serbia had found a mineral identified as having the chemical formula sodium lithium boron silicate hydroxide [1]. But instead of the large green crystals in Superman comics, the real thing is a white, powdery substance which contains no fluorine and isn't radioactive. The mineral, to be named Jadarite (after Jadar, the location of the Serbian mine where it was discovered), will go on show at the London Natural History Museum [2].

Forms of kryptonite

Variations

The various known forms of Kryptonite in the Superman comics:

Simulated kryptonite

Green Lantern Corps power rings can be used to emit simulated green kryptonite radiation. This radiation is apparently just as powerful and painful to Superman and other Kryptonians as the genuine rays but it can be blocked by interposing anything yellow between the Green Lantern's green kryptonite and the Kryptonian (however, this may no longer be an option due to the recent development of yellow no longer being an automatic weakness of power rings). Breaking the ring-bearer's concentration will also dispel the effect.

Synthetic kryptonite (usually the green or red variety) has been successfully produced by Lex Luthor, Batman, and Ra's al Ghul in the comics. It has proven to be less powerful than genuine kryptonite, to be extremely difficult to create, and to have a short half-life that renders it useless after a short period of time. In the Elseworlds story Batman: The Dark Knight Returns, Green Arrow wounds Superman with a synthetic kryptonite arrow, allowing Batman to defeat him. Bruce Wayne notes it was very expensive to develop. Superman III featured synthetic kryptonite that altered Superman's personality.

Magic: Individuals adept at the use of magic may be able to create kryptonite, such as Mr. Mxyzptlk did in the "Krisis of the Krimson Kryptonite" storyline (though his version of Red Kryptonite differed from the traditional version in its workings) Jimmy Olsen, when changed into a Genii in Superman's Pal, Jimmy Olsen #42 (January 1960), was ordered by his master, Abdul, to turn himself into Living Kryptonite, Jimmy chose Green Kryptonite.

On one occasion, Lex Luthor combined the element-duplicating substance that composes the robots known as the Metal Men into a single robot that imperfectly duplicated the properties of green kryptonite. While its presence caused Superman severe pain, it was not severe enough to completely incapacitate him, and did not affect his powers at all; thus, Superman was able to focus past the pain and defeat the robot.

Hoaxes

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

Silver Kryptonite: Featured in Superman's Pal, Jimmy Olsen #70, Silver Kryptonite is a hoax revolving around the silver anniversary of Superman's career. Silver Kryptonite in another form is a part of the Smallville TV series (see Smallville below), but NOT of the comics continuity.

Yellow Kryptonite: This one was used in a hoax masterminded by Lex Luthor.

Kryptonite Plus: 30 or so non-glowing, varicolored, banded rocks invading unnamed Super-aliens had left on Earth's moon and then said were Kryptonite Plus or maybe a form of Ultra-Kryptonite. They are really Tikron Stones. From Superman's Pal, Jimmy Olsen #126 (January 1970).

Purple Spotted Kryptonite: Mentioned in Streaky's fictional story in the animated cartoon Krypto the Superdog. This phoney Kryptonite makes Krypto chase his tail.

Fake Kryptonite: Seen in an episode of Superboy 1988 TV series, Superboy's friends are selling crystals which are labeled as "fake Kryptonite" to raise money for charity. These crystals are clearly false and the vendors make no dispute about it. However, they use humorous references such as "Buy one and have nothing to fear; even Superboy will run away from you!"

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.

Depictions of kryptonite in the various films and TV series of Superman have largely been limited to green kryptonite, with occasional appearances of the red and blue varieties.

Adventures of Superman

Kryptonite was used in several episodes of Adventures of Superman, proceeding from straightforward to increasingly far-fetched plotlines. The specific color is not definite, given that it is never mentioned and that the series was in black & white, but from its effects, it is presumed to be green kryptonite in all cases:

In "Panic in the Sky", Superman’s attempt to shift a meteor hurtling toward earth leaves him with amnesia. Although the scientists in the episode only say the meteor consist of "unknown elements", a fragment of this meteor is later used in The Deadly Rock, then referred to as Kryptonite.

In "The Defeat of Superman", an overacting scientist working for a crime boss synthesizes kryptonite after working out the formula from a tiny fragment found in a meteorite. As Superman lies dying from the metal's affects, Lois and Jimmy rescue him for once, sealing the block of kryptonite in a lead pipe, and Superman recovers. He then flings the pipe through the sky and into the sea with a super-throw. The escaping criminals, startled by the rocketing pipe, veer off the road and plummet to their deaths, keeping this dangerous secret "safe" in the hands of Superman's two friends.

In "Superman Week", Jimmy manages to blurt out the secret to the wrong listener. Superman stages an elaborate ruse in which he pretends to have retrieved the lead-encased metal from the ocean, and uses it to lead a wanted criminal into a trap. This ruse also presumably proves that Superman is not vulnerable to it, thus staving off criminals' thoughts of using it...for awhile.

In "The Deadly Rock", another eccentric scientist finds a meteorite that happens to be from Krypton, and a crime boss tries to use it to destroy Superman, who instead destroys it through the unlikely method of burning it with a flame-thrower.

In "The Magic Secret", yet another eccentric scientist teams with a criminal, this time tricking Superman into descending a narrow and deep well to rescue Lois and Jimmy, then proceeding to shower the Man of Steel with kryptonite particles.

In "The Gentle Monster", a very eccentric but good-natured scientist constructs a super-powered robot whose strength is derived from a chunk of the metal that the scientist has found, not knowing the danger it poses to Superman.

Movies

Kryptonite was featured in Superman: The Movie. In the film, Lex Luthor (Gene Hackman) and his cronies (Ned Beatty and Valerie Perrine) track a large chunk to Addis Ababa, Ethiopia, where they steal it from a museum under the cover of night. In this film's usage, the term "kryptonite" seems to mean simply a "Kryptonian meteorite". After co-opting and launching two nuclear missiles for opposite ends of the United States, Luthor places the kryptonite on a chain around Superman's (Christopher Reeve) neck and drops him into a swimming pool. When Perrine's character Miss Teschmacher learns that one of the missiles is headed for Hackensack, New Jersey (where her mother lives), she rescues Superman from drowning and removes the kryptonite, after which his strength and powers quickly return.

An imperfect synthesis of artificial kryptonite containing tar appeared in Superman III. Ross Webster (Robert Vaughn) orders the creation of synthetic kryptonite after remembering a Daily Planet story about the last original chunk disappearing years earlier after falling to Earth (whether Webster references the kryptonite robbery in Superman: The Movie is unclear.) Developed by Gus Gorman (played by Richard Pryor), it was intended to be a copy of Green Kryptonite. After scanning the coordinates of Krypton's former location via satellite, results return a small percentage of an unknown component. The substitution of tar (which Gorman used after glancing at a cigarette carton) for a crucial, but unknown, component resulted in the synthetic kryptonite behaving like Red Kryptonite and Black Kryptonite; in this case, the kryptonite turned Superman evil and eventually split him into two people. The evil Superman and Clark Kent, the embodiment of Superman's remaining good qualities, then engage in an epic battle at a deserted junkyard, where Clark emerges victorious and the evil Superman fades from sight. Later in the film, Gorman's creation, the Ultimate Computer, severely weakens Superman with a kryptonite ray before Gorman has a change of heart and attacks his own machine.

In Superman Returns, an additional piece of kryptonite is found in a rock fragment, once more in Addis Ababa. Lex Luthor steals it from a Metropolis museum and uses it in his quest to create a new kryptonite landmass, much like how young Clark created the Fortress of Solitude. In addition, he uses a shard leftover from processing it to create a kryptonite shiv, which he uses to stab Superman with at one point.

The Adventures of Superboy

Kryptonite made frequent appearances in the syndicated "Superboy" TV series, most of it green. It first appeared in the first-season episode "Kryptonite Kills" in which Professor Peterson retrieved it from Addis Adaba believing it to be a harmless meteorite and brought it to his gemology class at Shuster University. Superboy, a student in Peterson's class (as Clark Kent), collapsed from the radiation and felt its effects for the first time. He later threw most of the Kryptonite into space, except for one piece which was washed into the sewer. That piece was discovered by a mixed-up scientist who used it as a power source for Metallo (Roger Corben) in the second season episode "Metallo".

Green Kryptonite made several more appearances throughout the series, used mostly by Lex Luthor and Metallo. In the third season episode "Bride of Bizarro", Luthor sent Bizarro to a military research base to steal a large amount of Kryptonite, which Luthor was seen using on Superboy in later episodes. In the fourth season episode "Kryptonite Kid", a young man named Mike Walker working at the same military research base was caught in a Kryptonite explosion while working to find a cure which would make Superboy immune to the radiation. The Kryptonite entered his bloodstream and turned his skin green and he became "living, breathing Kryptonite" able to fire Kryptonite radiation from his hands. In "Obituary for a Super-Hero", Luthor used a Kryptonite bomb planted on a yacht to attempt to kill Superboy.

Red Kryptonite made an appearance in the second season episode "Super Menace". This version of Red K was created at a military research base where scientists were working to neutralize Kryptonite's effect on Superboy while still retaining its radioactive properties so it could be used as a power source. Their experiments turned the Kryptonite red, making it useless as a power source and altering its effect on Superboy. This Red Kryptonite turned Superboy evil, much like Red K would later do in the "Smallville" TV Series, except only a single exposure to it was required, rather than constant exposure. After Superboy wreaked havoc with Metallo, Lana tricked Superboy into being exposed to another chunk of Red Kryptonite which reversed the effects of the first. This is Red Kryptonite's only appearance in the series, so it is unknown if the substance would have had other effects on Superboy if it had appeared again.

The "Superboy" series also introduced a form of White Kryptonite, however this was not the white kryptonite that kills plant life (as seen in the Pre-Crisis comic books). This White K was created by Professor Peterson's duplicating ray in an attempt to create a form of Kryptonite that would kill the molecularly unstable Bizarro. This Kryptonite did not kill Bizarro, however. It instead had an opposite effect on him and actually stabilized and cured him, preventing him from eventually exploding as previous Bizarro duplicates had. White Kryptonite made only one appearance in the series in the episode "The Battle With Bizarro". It is referred to again in "The Bride of Bizarro" but it is not seen.

Lois and Clark: The New Adventures of Superman

Kryptonite was used throughout the 1990s television series Lois and Clark: The New Adventures of Superman.

In "The Green, Green Glow of Home" the first piece was unearthed on the Smallville farm of Kent family friend Wayne Irig. He sent a sample of the rock to a local university. This came to the attention of Jason Trask. Trask headed Bureau 39, a secret government organization that investigated perceived alien threats. Trask had the paranoid belief that Superman was the first agent of an alien invasion. Understanding that the radioactive meteorite came from Krypton, he attempted to use the rock to kill Superman. Subsequently the main fragment of the meteorite was destroyed and Trask was killed by the local Sheriff. Consequently only Clark Kent and his parents knew of its true existence. Clark and his partner Lois Lane reported on the incident in The Daily Planet and described Trask's delusions of a fabled rock that could kill Superman. Ironically in this article it was Clark Kent himself who first named it "Kryptonite".

As shown in "Barbarians at the Planet" and "The House of Luthor" The story of kryptonite intrigued Superman's archenemy Lex Luthor. He used the many resources at his disposal to track down and confirm the existence of the original sample that Irig had sent to be studied. Luthor ground down part of this kryptonite and used it to coat the bars of a cage to entrap the Man of Steel. After Superman's escape from this kryptonite prison and Luthor's apparent death, the legend of kryptonite continued to grow.

Many criminals and former Lexcorp employees sought to acquire Luthor's kryptonite. In fact most of the kryptonite to be featured on the series originated from that first chunk found by Wayne Irig. During the 3rd season a new second piece was discovered, which Superman turned over to S.T.A.R. Labs for testing. This was the source of most of the kryptonite featured for the remainder of the series.

On Lois and Clark, green kryptonite was delivered in a variety of ingenious ways. A bullet was fashioned from pure kryptonite in one episode, and in another, a wicked woman tried to bring about Superman's demise by kissing him after coating her lips with a kryptonite-contaminated lipstick. In the episode "Metallo", scientist Emmett Vale, who studied Luthor's kryptonite while working at Lexlabs, used a piece to power the cyborg he created from fatally wounded criminal John Corben.

Red Kryptonite also was featured in the series. In one episode, it made Superman apathetic; in another, it transferred his powers to Lois Lane after being focused through a laser beam. In yet another, it uncontrollably supercharged his powers, causing him to do things such as accidentally fly through the sidewalk when landing. A renegade S.T.A.R. Labs scientist created a "Hybrid Kryptonite," which has no effect on Kryptonians, but hurts humans.

Animated series

The 1970s and 1980s Super Friends animated series featured kryptonite in various episodes, usually green. In the episode "Rest in Peace", Sinestro refers to a form of kryptonite called "Krypton Steel" as "a harmless form of kryptonite that only Superman can penetrate". In another episode, "Darkseid's Golden Trap", gold kryptonite appears, which is stated to have an effective range of 20 ft (6.1 m). Blue kryptonite also makes an appearance in one episode; Superman, aging rapidly from exposure to Red Kryptonite, acquires a sample of Blue Kryptonite (which had been discovered floating in space) and uses it to cure himself (Blue Kryptonite has negative effects on Bizzaro, so it should have positive effects on Superman).

In the 1990s series, Superman: The Animated Series, one explanation offered for the science of kryptonite is that Superman feels the detrimental effects of kryptonite radiation quicker that normal humans because his body absorbs it more readily, as a result of sharing a common point of origin with the element. The effect is so potent that even a tiny shard is enough to painfully affect Superman at a short distance. This makes it impossible for Superman to even touch the substance, as it would be the equivalent of a normal man touching radioactive rods from a nuclear reactor with his bare skin. Only the element of lead is able to block the radiation, and is therefore Superman's only protection. Fortunately, Professor Hamilton supplies Superman with a distinctive and durable lead protection suit for such situations.

Kryptonite, in the animated series, still has effects on normal humans as well. Two moments are evidence of this. First, the "Jade Dragon" from The Batman/Superman Movie (a crossover between The New Batman Adventures and Superman: The Animated Series) is a statue of kryptonite carved in the form of a Chinese dragon, said to be cursed because all of its owners all died within a few years of acquiring the piece. Second is Lex Luthor's kryptonite poisoning/cancer as seen in Justice League, attributed to Lex's admitted habit of keeping a fist-sized chunk of kryptonite in his pocket for years. This does bring up the question of Batman's habit of also carrying a piece of kryptonite in his own belt; however, since Batman has seen what the kryptonite did to Luthor, the famed methodicality of Batman may mean that he likely has the pouch lined with lead. In Batman Beyond, it was revealed in the two part episode "The Call" that Bruce Wayne kept the kryptonite for the rest of his life, and kept the needle of kryptonite locked up very securely in the Bat Cave. The Justice League series also reveals how Batman obtained the kryptonite.

Green kryptonite remains the only variety of the substance ever seen in the DCAU.

As mentioned above, the Krypto the Superdog episode "Streaky's Cat Tail" features "purple-spotted kryptonite", which causes Superdog to compulsively chase his tail. However, this was almost certainly a product of Streaky's imagination. Red Kryptonite has appeared and is stated as having weird effects on Kryptonians for a day; it has swapped the minds of Kevin and Krypto, and removed Krypto's powers. Kryptonite also appears in an episode of the Legion of Super Heroes cartoon, where it is revealed Brainiac 5 has a piece of it, and that the villain Drax, who, despite being an analogue to Superman, is immune to it.

Smallville

In the 2000s television series Smallville, the show expands on the concept of the substance being harmful to humans, as well as making extensive use of the substance. On the show, not only is green kryptonite (referred to in the first two seasons of the series as "meteor rock") harmful to Clark Kent, but it can produce bizarre changes in humans, animals, and plants, 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 circumstances under which the subject was exposed to kryptonite and the subject's emotional state (similar to how gamma radiation affects people in the Marvel Comics universe). Groups of people have been shown to acquire the same powers from kryptonite by exposing themselves to it in the same manner. It is interesting to note that exposure to kryptonite among Caucasians causes them to gain superpowers while prolonged exposure to kryptonite among African-Americans causes them to have involuntary spasms and seizures (as evidenced in the episodes "Jitters" and "Duplicity"), though this is never explicitly stated, and thus is probably coincidental.

The harm inflicted on Clark by kryptonite on Smallville is varied. He cannot be near green kryptonite without doubling over in nausea and pain, and if he were to hold a fragment of it in his hand, it would burn to the touch and the veins in his hand would become exposed and green. However, on other separate occasions Clark has held and even ingested kryptonite (albeit in dilluted form) and been merely weakened. When a vial of Clark's blood was held up to kryptonite to verify its authenticity, the blood began to boil.

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 is capable of separating certain entities within individual organisms, e.g., splitting a person's good and evil sides. Black kryptonite was formed by heating up green kryptonite. In the series, after Clark's "reprogramming" by Jor-El in the caves, Martha Kent used black kryptonite to reveal the two psyches of Clark, the militant Kal-El (not to be confused with the rebellious "Kal" alias caused by red kryptonite), and normal Clark. In a later episode, Lex Luthor was experimenting with a process to heat up green kryptonite and irradiate seeds, in order to separate the "weak" genes from the "strong" genes in the seeds. The result was hardy but rotten-tasting fruit, implying a yin and yang balance within fruit, as well as within humans. An accident with this process caused Lex to split into a good Lex and a bad Lex who referred to himself as "Alexander".

Silver kryptonite made an appearance in the fifth season episode entitled "Splinter". Like the previous comics incarnation, this silver form was not a true form of the stone. In the episode, Clark pricked his finger on a rock that was black and had silver-metallic clusters, and subsequently became increasingly paranoid, hallucinating that others were conspiring against him. In the episode's final scenes, it was revealed that a splinter of the element entered Clark's bloodstream. It was also shown that silver kryptonite was created artificially from the liquid metal which forms Brainiac's body.