Silver Kryptonite (or fake Kryptonite) was used to keep Superman from closely investigating what turned out to be a 25th silver anniversary gift for him from his friends, in honor of his arrival on Earth.
Silver Kryptonite induces hallucinations and paranoia into a Kryptonian, as seen in Smallville, Batman and Superman Adventures.
Apparently it was made by a mad scientist , who had some green Kryptonite and added methane gas, and various other drugs.
In "Smallville", Clark saw his family plotting against him, but he was just under the effects of Silver Kryptonite,
In other Appearances it has been called fake.