Nova, Vol. 1 #3 (1976)

-- The Deadly Diamondhead Is Ready To Strike!
Nova gets wind of a new villain on the loose, calling himself Diamondhead. When they face off, he learns that Diamondhead truly is made of diamond, making the battle far more difficult than anticipated. Worse yet, Diamondhead has stolen evidence that Powerhouse had in his possession when he was captured in the last issue.
Release Date: 1976