His name is Stoner. Mark Stoner. He's a treasure hunter and a salvage expert based in Key West, but THE SATAN STONE, the second Stoner adventure penned by Ralph Hayes, is set in Africa.
Published by Manor in 1976, THE SATAN STONE starts out with a different character carrying the first two chapters. McMillan, a so-called partner at a South African diamond mine run by the fat, corrupt De Villiers, is cheated of his final payment. Hey, what can he do about it, seeing as De Villiers' vicious right-hand man Graaf has no qualms about torturing and killing anyone who even slightly threatens his boss.
So McMillan decides to steal the largest diamond he's ever seen. Easily a million-dollar gem. But there's no way to get it out past Graaf's security, so he stashes it beneath a bulldozer. McMillan avoids being killed by one of Graaf's men and makes it to Nairobi, where he runs across his old friend Mark Stoner. And eventually--with some fast talking--convinces Stoner to infiltrate De Villiers' camp and somehow emerge with the gigantic gem.
Air Force veteran Hayes does a nice job spinning this tough-guy yarn, which may remind one somewhat of the 1976 action film KILLER FORCE. The macho shenanigans and action sequences are rendered in an exciting manner, just like a pulpy short story out of a sweaty men's magazine. The climax finds Stoner stranded in the desert and pursued by some of De Villiers' men...who are slightly less dangerous than the pack of killer baboons who attack him!
I liked the one Hunter novel Hayes wrote, and this is a good one too. Hayes also wrote the Cominsec series and a few Nick Carter adventures.