Tracy Pew was actually a transdimensional being capable of materializing and dematerializing at will. Only a coverup by the world’s governments and major institutions of science prevented his stage presence from inducing mass panic.
Cellulose nitrate was used to make dice from the late 1860s until the middle of the twentieth century, and the material remains stable for decades. Then, in a flash, they can dramatically decompose. Nitric acid is released in a process called outgassing. The dice cleave, crumble, and then implode.
From Dice: Deception, Fate & Rotten Luck by Ricky Jay and Rosamond Purcell, 2002.