And, in what is harder for a secretive company like De Beers, opening the diamond area means relaxing security. The company will have to concede the existence of roads that aren't on maps and leash the ''ruthless well-armed guards'' the guidebooks warn of. Someday, there may even be a hotel more interested in a tourist's credit card than his criminal record.

At the moment, though, security is still obsessive. Sweepers toil under the distant lenses of weatherproof cameras. Sorters hold their tweezers by a glove built into a glass box and drop jewels into vacuum pipes that suck them to a vault. A visitor who bends down to pick up a scrap of litter risks arrest -- mere possession of a rough diamond is a 15-year prison term.

On the way out, visitors and workers file through human cattle pens, push open doors when green lights click on and finally meet guards who minutely search their clothes, pick out the gravel caught in their shoe soles and give them a full body X-ray. (To prevent overdoses, workers have X-ray history cards and cannot tell when the X-ray machine is scanning them or faking it.)

Since the average size of the diamonds near the Orange River mouth is one carat, theft is a huge temptation. Miners have been caught with diamonds in ears, noses and everywhere else. They have shot them over the dog-patrolled fences by crossbow. When one technician, Lucas van der Merwe, was working on an electrical tower, he caught a homing pigeon wearing a tiny hand-sewn jacket with 123 diamonds in it. Knowing the alternative was life in prison, he turned it in, earning a nice bonus.

[On April 19, four men were arrested in Alexander Bay, South Africa, on charges of using racing pigeons to smuggle diamonds out of the Forbidden Area, local newspapers reported. Three dozen small uncut diamonds worth $6,000 were seized.]

To prevent anyone from slipping diamonds into gas tanks or truck frames, no piece of equipment that enters the mine ever leaves. The company's earth-moving fleet was once second only to the United States Army's, and executives used to proudly show off the vast parking lot where every digging machine and truck used since the 1920's sits rusting. Now, sensitive to its environmental image, the company refuses to let the vehicles be photographed.

''They'll probably be melted down someday,'' said Dries Olivier, a mine manager.

But fear stalks the beaches too. Any miner who spots a diamond on the ground gets 70 percent of its value for turning it in, said Mr. Ward, the geologist. But no miner has turned one in since 1983. The smuggling syndicates ''have crueler incentives, like breaking legs, to get people to not turn them in,'' he said.