In Smallville, there were several different forms of kryptonite, and each one had a different effect on Clark (Tom Welling) and other members of his species. Just like its comic book counterpart, Smallville’s kryptonite is a mineral from the character’s home planet, as well as his greatest weakness.
It was made clear early in season 1 that Smallville is abundant with kryptonite. It came to the town in the meteor shower that brought baby Kal-El to Earth, though it was shown later that some kryptonite was already on the planet. For all of season 1, they were simply referred to as green meteor rocks. It wasn’t until season 2 when Clark met Dr. Virgil Swann (Christopher Reeve) that he learned its proper name: kryptonite. After that, the term was frequently used by characters in his inner circle who knew the truth about Clark's origins.
Kryptonite was arguably the show’s most important plot device, and not just because it’s known for being able to kill Superman. Characters like Lex Luthor (Michael Rosenbaum) understood that it had valuable properties and often used it in scientific experiments. It also gave superhuman abilities to numerous, single-episode antagonists that Clark tangled with throughout the series, particularly in his high school years. Primarily, the problems Clark and his friends had to deal with were related to just one form of kryptonite, but over the course of the show’s ten-season run, they discovered that there are actually multiple colors of the meteor rock. This is right line with the comics, which were packed with various forms of kryptonite. Here’s every kind that existed in Smallville, and how they affected Clark.
Green Kryptonite
The most common type is, of course, green kryptonite, which is the one most people are familiar with. Like the comics' Superman, Clark is greatly weakened whenever it’s nearby. Before knowing about his alien heritage, Clark suffered from its effects in his daily life whenever he would approach Lana (Kristin Kreuk), who wore a kryptonite necklace. Whenever Clark is near these rocks, he feels weak and sick. He typically collapses if it gets too close to his body. When exposed, he’s susceptible to serious injuries. Once it’s removed from his presence, Clark only needs a few moments to recover. This is also the form of kryptonite that has the capability to enhance humans with a wide variety of superpowers. Usually, these powers were gained by exposure to the rocks during the meteor shower, and the abilities they obtained were often related to where they were and what they were doing. For instance, Sasha (Shonda Farr) was able to control bees because she was stung by bees who lived in a meteor-infected hive.
Interestingly, Clark learned in season 2 that’s its possible for the green meteor rocks to lose not only their color, but their special properties (including their ability to hurt him). In one episode, Clark was rendered helpless by Lana’s necklace until his spaceship emitted a blast of energy that neutralized the kryptonite and gave it a new, clear look. As a result, Lana’s necklace is now harmless to Clark.
Red Kryptonite
It was discovered in season 2 that not all the rocks from the Smallville meteor shower were green. One kind is actually red in color and has a fundamentally different effect on Clark. After putting on a class ring with a gemstone made from red kryptonite (nicknamed “Red K”), Clark began to embrace his dark side. He took on a “bad boy” persona, talked back to his parents, and nonchalantly admitted to having feelings for Lana. All of these things happened because it made Clark let go of all his inhibitions. The class ring had to be destroyed in order to revert Clark back to his normal self, but it wasn’t the last time red kryptonite turned his life upside down. There were other, similar incidents that occurred in later episodes.
It was revealed in season 6 that it is possible for humans to be influenced by it as well, but not in the same way. When Lois wore lipstick that contained Red K, she immediately developed an intense love for Clark that severely impacted her ability to think rationally.
Black Kryptonite
In the Smallville season 4 premiere, Clark was being controlled by the Kryptonian side of his personality, Kal-El, who Jor-El wanted to use to gather the Stones of Power. To make Clark go back to normal, Dr. Bridgette Crosby (Margot Kidder) gave Martha Kent (Annette O’Toole) a black kryptonite rock. With it, Martha succeeded in splitting Clark into two different versions of himself. Clark had to defeat Kal-El in order to regain complete control over his body. Later in the season, two important revelations were made about the nature of black kryptonite, with one being that it can be created by heating the green kind to an extreme temperature. Also, the effect that it has on Clark is similar to what it does to humans. When Lex Luthor was exposed, he was split into his good and dark sides. One Lex possessed only his positive traits, while the other was pure evil. In the season 8 finale, it returned to serve as Clark’s secret weapon against Doomsday, as this was how he separated the monster from his human alter ego, Davis Bloome (Sam Witwer).
Silver Kryptonite
In a season 5 episode, Brainiac (James Marsters) anonymously gifted Lana with a piece of silver kryptonite knowing that it would eventually catch Clark’s notice. When Clark held it in his hand, a piece of it broke off and gave him a splinter. As a result, Clark began to experience paranoid delusions. Due to the silver kryptonite in his system, Clark felt like everyone in his life was turning against him. It even reached a point where Clark became violent toward those he believed had betrayed him.
Blue Kryptonite
In season 7, Clark met Dax-Ur (Michael McClure), a Kryptonian scientist living a normal life with a human family. He was able to accomplish this by wearing a watch adorned with a piece of blue kryptonite. Instead of weakening Kryptonians, the blue variation negates their powers for as long as they’re in physical contact with it.
Gemstone Kryptonite
Clark encountered a new form of kryptonite in season 9 when a woman blew pixie dust on him. Unbeknownst to Clark, the dust was really gemstone kryptonite, which temporarily gave him a new power. People became mentally compelled to act on any wish that he spoke aloud. Affected victims were willing to do whatever it took to follow through on fulfilling Clark’s requests. He also accidentally used this ability on himself. Momentarily wishing to be “a killer” like Zod nearly drove him to murder.
Gold Kryptonite
There was one type of kryptonite in Smallville that Clark never came in contact with, but if he had, his story would have come to an abrupt end. It’s been said that while the blue kind negates their powers, gold kryptonite takes them away forever. It was used as a weapon against him in season 10, but fortunately, he was able to avoid touching it. However, it appears that even though Clark managed to stay away from gold kryptonite in Smallville, he did end up using it purposely after the show ended. It’s believed that this is what allowed Clark to rid himself of his powers prior to Superman's “Crisis on Infinite Earths” cameo.