BIOGRAPHY
Jack Winters was once an employee at a nuclear power plant when his gambling debts made him turn to crime. Late one night, he snuck into a lab to steal some regulated radioactive materials and sell them for a profit. A batch of isotopes became unstable as he handled them, exploding in his grasp and causing severe radiation burns. Although he managed to hide the reason behind his injury, Jack still spent weeks in the hospital recovering as his heavily bandaged hands tried to heal.
As he recuperated at home, Jack removed his gloves and bandages to discover his hands had mutated into a form of flexible, living diamond. He also developed other amazing abilities, including telepathy and teleportation. Reasoning that his changes were the result of the radiation he was exposed to, “Jack O’Diamonds” plotted to break back into the plant and absorb more radiation to become even stronger. As he made preparations, Jack detected another mutant brain nearby and psychically summoned the stranger. Jack Winters met Scott Summers, a teenager on the run from the orphanage and the police, ever since his optic blast caused an incident in the city. Jack O’Diamonds eagerly embraced his fellow mutant as a partner for his crimes.
Jack’s lust for power gave him enough charisma and self-confidence to draw the confused teenager into crime without asking too many questions. As it happened, however, Professor 
Charles Xavier was already on Scott’s trail when he met Jack O’Diamonds. At the nuclear plant, Xavier confronted the duo and offered Scott another path. The young man refused to turn his eye beams on another person like Jack commanded. However, Jack’s own mental powers allowed him to resist Xavier’s attempts at telepathically stopping the criminal. Jack’s raw strength broke the stalemate between the two psychics, causing the ceiling to collapse and separate them. Jack wanted to gain access to the plant’s main cyclotron, but Scott refused to help him any further. Jack pressed on alone and operated the cyclotron’s controls, giving himself a massive dose of radiation. Jack O’Diamonds was no more as his entire body changed to become the Living Diamond.
Drunk on his power, the Living Diamond attacked Professor Xavier and Scott with his new strength. Thanks to his transformation, Jack was not only stronger but also even more resistant to Xavier’s telepathy. Xavier and the teenager fled into a nearby building, which contained an ultra-sonic vibration inducer engineered to test the isotopes. They lured Jack into the inducer’s beam, with the hopes of immobilizing the Living Diamond within the vibrations. Jack struggled against the beam’s effects, despite Xavier’s warnings, and soon disappeared in a burst of raw energy. Scott and Xavier believed the vibrations had torn Jack apart due to his struggling, blasting him to atoms. [X-Men (1st series) #39-42]
In actuality, Jack detected the vibrations’ threat and tried teleporting himself to safety. During transition, his atoms were picked up by an experiment conducted by Department H, drawing him to re-materialize in their care. Colonel Bernardo and H recruited Jack O’Diamonds as a field agent, and he went along with them as the department’s scientists helped to increase the range of his teleporting powers, among other things.
The Living Diamond teamed up with Department H’s other active field agent Weapon X, also known as the Wolverine. Department H detected a large assortment of mutants gathered by the Secret Empire, [Captain America (1st series) #174-175] and tracked two of them to the Brand 
Corporation on Long Island. Their mission was to recruit these “extra-normals” as new agents for the program. Jack and Wolverine did not like each other, or their supervisors, and came to blows almost immediately after Jack teleported them to the States. The Living Diamond was surprised to learn that Wolverine’s Adamantium claws were strong enough to pierce his skin, but Jack’s self-healing structure made Logan’s claws a nuisance at best. Caught in a stalemate, the two men put aside their differences to continue the mission.
Inside the Brand Corporation, they discovered Mesmero and the Beast, hypnotically conditioned to be Mesmero’s friend and partner, “Wildlife.” They intended to steal the electron-gyro, which Brand had engineered for the Secret Empire. The two duos fought with each other and with Linda 
Donaldson, a Brand double agent sent to acquire the gyro for the Empire. When the Living Diamond prepared to murder Linda for getting in his way, Wolverine interceded and stabbed Winters again. This time, Weapon X kept Jack impaled on his claws, while vibrating them until the feedback completely disrupted Jack’s molecular integrity. The Living Diamond ended up shattering like glass, leaving behind no trace of the criminal. [X-Men: Legends (2nd series) #1-2]
Somehow, enough of Jack Winters remained to be buried, albeit in an unmarked grave in Potter’s Field. Many years later, the New Orleans houngan known as the Black Talon made plans to 
assemble a group of undead mutants as his zombie servants known as the X-Humed. The Living Diamond rose from the grave along with Harry Leland, Changeling and Scaleface under the voodoo priest’s control. Circumstances conspired to have She-Hulk intervene on the Talon’s plans, however, and he failed to exert enough control over his zombies to direct all of them in a fight simultaneously. The Changeling retained enough free will to act against Black Talon’s schemes and he was soon defeated, returning Jack Winters and the others to their rest. [Sensational She-Hulk (1st series) #33-35]
[Note: Mutant or not? Jack Winters got his powers after being exposed to radiation. He later increased his powers by exposure to the same radiation. Typically, that’s not how mutant powers work. On the other hand, Xavier’s Cyberno device registered Jack O’Diamonds as a mutant presence along with Scott. It’s possible Cyberno was less discerning as a prototype than its successor Cerebro, or maybe Jack’s psychic powers came from his X-gene and the diamond powers were radiation based.]