The Zero Stone by Andre Norton cover by John Raynes (1977)
I was in bookshops in 1977 and looking at Sci-fi but although I know this cover caught my eye back then, I never made the leap of putting my hand in my pocket in order to buy a copy. As such I've no idea if its any good or if the cover is representative of the story within. However I do know that it's rather brilliant and, in combination with that font, absolutely spot on a commission for the time.
First published in 1968, this is the clean art and the finished cover of the Beaver Books edition.