In December 1979, Jacqueline Kennedy Onassis was photographed at a fund-raiser for her brother-in-law at the Pierre Hotel in New York with Maurice Templesman, an international diamond merchant and mining tycoon.

Almost no one who knows them was surprised. The 50ish Tempelsman -- a man who could end up being richer than Aristotle Onassis if all his global dealings go through -- was a friend and supporter of John F. Kennedy's in the 1960s.

A politically powerful and secretive man, Tempelsman heads one of the world's largest minerals consortiums comprised of investors from the United States, France, South Africa and Japan. He is a close personal friend and business associate of Zaire's President Mobutu Sese Seko and reportedly had a say in the Carter administration's appointment of a new U.S. ambassador to the country.

Over the past five years, the widowed former first lady has been seen in public form time to time with the portly, 5-foot-7 Templesman. No one but the supermarket tabloids has paid much attention.

Then, last month, on May 14, Mrs. Onassis and Tempelsman flew into Savannah, Ga., for a holiday aboard his waiting motor yacht, the "Relemar."

The trip has focused new attention on an old friendship.

According to a Savannah travel agency, Templesman's secretary in New York made arrangements for the couple to be met by a limousine for a guided tour of the city's historic buildings and antique shops.

Mrs. Onassis and Tempelsman stayed aboard his yacht, attended by a crew of two. The dockmaster at the Thunderbird Marina, where Templesman's boat tied up, said yesterday that the "Relemar's" captain had brought the vessel down from New York and was bound ultimately for Fort Lauderdale. t

But the "Relemar" put into port again down the coast at Beaufort, S.C., on Friday and spent the night at the Downtown Marina. On Saturday morning, a Savannah newsman assigned to try to get a picture of the couple together said that Mrs. Onassis and Templesman came ashore in the rain, and headed for an 18th-century church that is one of the city's architectural landmarks.

Mrs. Onassis ducked behind Templesman in an apparent attempt to avoid the camera. The photographer persisted in following them, and they returned to the yact and departed from the marina a short time later.

Friends of Mrs. Onassis and Tempelsman have been aware during the last 18 months that they have been seen together with increasing frequency.

Tempelsman, married and the father of three children, said in a telephone interview yesterday that recent talk about his relationship with Mrs. Onassis is "highly exaggerated."

When asked if he is separated from his wife or contemplating divorce, he said "no."

"We're just not going to talk about this", he said. "Let's leave it at that."

He declined to comment on reports that he and Mrs. Onassis have traveled together abroad several times recently, including trips to Paris and the French side of the Caribbean island of St. Martin.

"We've known each other for a long, long time," he said. "Thats all I'm willing to say."

Tempelsman is a man who likes to operate without a lot of publicity. He has important political ties with both the Republicans and the Democrats. hIn 1972, he was one of the "secret" contributors who gave money to Richard M. Nixon before federal disclosure laws took effect.

According to a Washington Post story on Dec. 19, 1979, Tempelsman had a say in the Carter administration's appointment of the new U.S. ambassador to Zaire. According to the news account, Tempelsman is a close friend and business associate of Zaire's President Mobutu Sese Seko.

Tempelsman put together a consortium that owns 80 percent of the world's richest copper and cobalt lode which lies beneath 900 square miles of Zaire's mineral-rich Shaba Province.

The consortium of investors from the United States, France, South Africa and Japan.

Tempelsman "grew up in African metals" as a salesman, middleman and investor, working for his father in the New York firm of Leon Tempelsman and Son.

With Mobutu, Tempelsman is also a major force in the world's industrial diamond trade and gemstone diamond traffic.

A State Department source said yesterday that Tempelsman is also "heavily into diamonds in Sierra Leone."

He also owns a company in Dallas, Tex., which manufactures drills for oil rigs.

Tempelsman and Mrs. Onassis share an interest in history and all things ancient. He is said by friends to have a collection of classical antiques that rivals those of the world's major museums.