The origins of kryptonite can be traced back to the first "Superman" story by Jerry Siegel and Joe Shuster. "The Reign of the Superman" was printed in Science Fiction: The Advance Guard of Future Civilization #3 (January 1933). Professor Ernest Smalley discovers a meteorite from a "Dark Planet." After ingesting a few grains, a vagrant named William Dunn is granted vast intelligence, telepathic powers, and the ability to "intercept intergalactic messages." Dunn murders Smalley and plans to destroy civilization, but the effects fade before the source element can be reached.

Krypton (Kr), atomic number 36, is a chemically inert noble gas. Krypton is colorless, odorless, and tasteless, occurring in trace amounts in the Earth atmosphere. The word is derived from the Greek kruptos meaning "hidden." The element was discovered in 1898 by Scottish chemist William Ramsay and English chemist Morris Travers. In 1904, Ramsay was awarded the Nobel Prize in Chemistry for his discoveries.

The fictional planet of Krypton first appeared unnamed in the opening panel of Action Comics #1 (June 1938). The names Krypton and "kryptonite" first appeared in an advertisement for the Daisy Krypto-Raygun in Action Comics #8 (January 1939), on sale November 25, 1938. "Looks exactly like the KRYPTO-RAYGUN Superman had made of KRYPTONITE, the amazing metal from his birthplace – the weird Planet KRYPTON!" The toy functions as a film projector for seven different 16mm Superman comic strips. The Krypto-Raygun was later offered as a premium from Superman Gum.

An early prototype of kryptonite appeared in an untitled and unpublished 26-page story by Jerry Siegel. Professor Barnett Winton identifies "K-Metal" as a meteorite from Krypton. The metal weakens Superman and allows him to feel pain, leading Clark to deduce that Krypton is his home planet. Clark reveals his identity to Lois and they decide to become partners, but she resents him for keeping the secret. The story would have ended the love triangle that defined early Superman mythology. A note from editor Whitney Ellsworth suggested specific changes to the script, but the Lois reveal was seemingly approved.

In 1970, four finished pages of the story were published in The Steranko History of Comics, Vol. 1. A carbon copy of the script was discovered in the DC archives by Mark Waid on Thanksgiving Eve of 1988. The typed cover page to Jack Liebowitz contains a handwritten date of August 7, 1940. Jerry Siegel did not remember the story, but he was known to purchase Superman plots from ghost writers. Some of the artboards by Joe Shuster, Paul Cassidy, and Wayne Boring are held in private collections.

The story has become known as "The K-Metal from Krypton" after a reference by author Gerard Jones in 2004. Artist Alex Ross pitched a recreation painted in the style of Shuster, but the idea was rejected by DC. The known remnants of the story have been reconstructed by members of the Superman Through the Ages! website.

-

The Adventures of Superman radio series introduced kryptonite in "The Meteor from Krypton," first broadcast June 3–11, 1943. The seven-part storyline was written and directed by George Lowther. At the Metropolis Museum, Dr. John Whistler identified kryptonite based on previous observations of Krypton's destruction. The metal "glowed like a green diamond" and weakened Superman within ten feet. The meteorite caused Superman to see visions of Krypton and his parents, Jor-el and Lara. "I know now, for the first time, who I really am, where I came from." The radio series established lead as the only substance that shields the deadly kryptonite radiation.

The original spelling of "Jor-L" is an anagram of Jerome Siegel. The name was first published in a "Federal Men" story by Siegel and Shuster in New Adventure Comics #12 (January 1937). The names Jor-L and Lora would later appear as the biological parents of Superman in the January 16, 1939, newspaper strip. The names were later spelled as Jor-el and Lara in The Adventures of Superman novel by Lowther, published on November 2, 1942.

-

Kryptonite first appeared on film in Superman starring Kirk Alyn and Noel Neill. The 15-part serial was released on January 5, 1948. In chapter four, "Man of Steel," Professor Arnold Leeds identifies a glowing meteorite as a fragment of Krypton. Exposure to kryptonite causes Clark to collapse, leading him to reveal the secret identity to Professor Leeds. The kryptonite is later stolen by the Spider Lady.

The sequel Atom Man vs. Superman was released on July 20, 1950. Luthor creates a synthetic kryptonite from plutonium, radium, and other elements. Luthor studied Krypton for years, piecing together data from astronomers. Before the planet was destroyed, Jor-El transmitted distress messages that were later deciphered by Luthor. After being exposed to the artificial kryptonite, Superman is captured and teleported to an early Phantom Zone known as "The Empty Doom."

-

The first comic book depiction of kryptonite is a glowing red gemstone in Superman #61 (November–December 1949). "Superman Returns to Krypton!" was written by Batman creator Bill Finger and illustrated by Al Plastino. After being weakened by the red meteorite, Superman travels backwards through time and space to trace the origin. He arrives on Krypton as an invisible observer and learns his origin for the first time.

Jor-El predicts the uranium core of Krypton will create a critical chain reaction. As the planet begins to collapse, Jor-El places his infant son into a rocket ship. His wife Lara chooses to stay on Krypton. The rocket lands on Earth and an "old couple" names the child Clark Kent. Superman concludes, "All the atomic elements fused to become one deadly compound!" The Kryptonian people are also referred to as "Kryptonites."

Kryptonite is first depicted as green in Action Comics #161 (October 1951). "Exit – Superman!" was written by Bill Finger, penciled by Wayne Boring, and inked by Stan Kaye. A group of bank robbers launch Superman in a rocket ship lined with kryptonite and lead.

Kryptonite was first mentioned in the Superman Sunday strip on April 6, 1958. Cosmic rays and kryptonite gas cause a chimpanzee named Big Boy to grow into a giant with kryptonite vision. The King Kong inspired storyline was a prototype for "Titano, the Super Ape" in Superman #127 (February 1959).

In Adventure Comics #255 (December 1958), red kryptonite from Mars causes Superboy to split into two beings. The duplicate is an evil Clark Kent that later destroys himself. Red kryptonite would later produce a different random reaction after each exposure.

The Achilles' heel plot device became a common gimmick throughout the Silver and Bronze Ages. Petty crooks could easily acquire an irradiated chunk of Krypton. A wide variety of kryptonite would be introduced to the Superman titles and each color effect varied for Kryptonians, humans, and animals. In Action Comics #261 (February, 1960), Streaky the Supercat was accidentally exposed to X-Kryptonite and given temporary superpowers.

In Superman #233 (January 1971) by Denny O'Neil, all kryptonite on Earth is transmuted into harmless iron. The "Kryptonite Nevermore!" era would end in Superman #288 (June 1975), and the array of colors would soon return. Following the Crisis on Infinite Earths in 1986, kryptonite was established as a compound rather than a transuranic element.

Kryptonite was reintroduced in Superman #1 (January 1987) by John Byrne. After locating the Kryptonian birthing matrix, Professor Emmet Vale discovers a glowing green meteorite. Lex Luthor later retrieved the two-pound chunk from the body of Metallo. Fragments of the compound were used to create bullets and a ring worn by Luthor.

The radiation would eventually cause Luthor to develop terminal cancer. Following the amputation of his right hand, Luthor transferred his brain into a younger cloned body. The ring was kept secure in the Batcave as a contingency plan.

In Superman #22 (October 1988), Superman uses gold kryptonite from the Pocket Universe to depower the Phantom Zone criminals. Superman exposes General Zod, Quex-Ul and Zaora to green kryptonite, causing all three to die. Overcome by guilt, Superman later exiles himself from Earth.

Kryptonite is a central part of Superman Returns, released on June 21, 2006. The Metropolis Museum of Natural History holds an Ethiopian meteorite specimen from 1978, the release year of Superman: The Movie. The meteorite is labeled as sodium silicate hydroxide, lithium, boron, and fluorine. Without the addition of fluorine, the chemical composition is similar to Jadarite.

Jadarite was found in a drill core from the Jadar Basin of Loznica, Serbia, in December 2004. The compound was identified by minerologists at the London Natural History Museum in late 2006. Dr. Christopher J. Stanley discovered the kryptonite coincidence while searching the formula on the internet. Jadarite is a dull white color and it does not exhibit any odd behavior on life from Earth.

-

Eury, Michael. The Krypton Companion. TwoMorrows Publishing, 2006.

Fine, Herbert S. [Jerry Siegel]. "The Reign of the Superman." Science Fiction: The Advance Guard of Future Civilization, vol. 1, no. 3, January 1933, p. 4–15.

Grogan, Walt. "Liberty and Justice: The Alex Ross Interview." Alter Ego, vol. 3, no. 30, November 2003, p. 3.

Hayde, Michael J. Flights of Fantasy: The Unauthorized but True Story of Radio & TV's Adventures of Superman. BearManor Media, 2009.

Jones, Gerard. Men of Tomorrow: Geeks, Gangsters, and the Birth of the Comic Book. Basic Books, 2004, pp. 181–183.

"'Kryptonite' discovered in mine." BBC News, 24 April 2007.

Murray, Will. "The Kryptonite Crisis." Alter Ego, vol. 3, no. 37, June 2004, pp. 18–31.

Stanley, Christopher et al. "Jadarite, LiNaSiB3O7(OH) a new lithium sodium borosilicate mineral from the Jadar Basin, Serbia." European Journal of Mineralogy, vol. 19, January 2007, p. 575.

Steranko, Jim. The Steranko History of Comics, Vol. 1. Supergraphics, 1970, p. 35.

"The K-Metal from Krypton." Superman Through The Ages, 2007, theages.superman.nu/k-metal/splash.php.

Thomas, Roy. "'K' is for 'Krypton'." Alter Ego, vol. 3, no. 79, July 2008, pp. 18–24.