When Mayor Marion S. Barry showed up at the White House recently wearing a small pin -- a black outline of the United States recessed into a silver silhouette of the African continent -- Vice President Walter Mondale peered closely and asked about its origins.

It was a Muntu medal, which in Swahili means "soul" or "essence of mankind," and in the jewelry market, is a new line that's taking off as a symbol of the black American line with Africa.

The medal is also worn by NAACP Executive Director Benjamin Hooks, labor leader William Lucy, civil-rights lobbyist Yvonne Price and, occasionally, by U.N. Ambassador Andrew Young and Mayors Ernest Morial of New Orleans, Maynard Jackson of Atlanta and Coleman Young of Detroit.

Ten years ago, many blacks were in-spired by the stormy civil-rights struggle to don flowing dashikis, adopt the colors of red, black and green, and wear medallions of clinched fists as symbols of black identity and cultural pride. Such symbols were largely relinquished during the 1970s. Still, some blacks quest for a symbol, and the Muntu is for them a statement.

Its creator, Sam Lax, is a white former San Quentin Inmate, who is now a Los Angeles-based jewelry maker and photographer. It is a sign of the times -- some would say sophistication -- that most wearers and promoters seem not to object.

Mayor Barry owns three Muntu lapel pins and calls them "an expression of solidarity with my African brothers and sisters in general and with the liberation struggle of people in South Africa in particular."

The jewelry also is gaining mileage from a current charity drive for the NAACP. Lax convinced the Pillsbury Co. to substitute its usual advertisement in the weekly black press with a plug for a Muntu-NAACP drive. Lax says he is contributing 50 cents of every dollar (the retail price is $12.50) to the civil rights organization.

"We judged Lax's sincerity by the amount of time and energy he puts into it and the commitment of his resources," said NAACP spokesman Paul Brock.

Ray Eiland, a Pillsbury vice president, said, "I think the project is fantastic. Lax calls up and says he loves me, he calls himself a son of a black revolutionary. I respond and don't question the idea of a white creating a symbol for blacks."

Lax. 45, is a tall, bony man who prefers the look of the old West, Levi's shirt and jeans, a fleece-lined vest and a silver blet buckle of horses, his own design. His voice and manner tend to-ward the agitated.

As he paces around his Los Angeles office, a converted dry-cleaning plant that is the headquarters of his company, SALA and Associates, his circuitous story is one of a latter-day believer, unaware of discrimination problems until one riveting experience and now driven to grandiose displays of brotherhood. He calls Yvonne Price "my sister" and Benjamin Hooks "Dr. Ben."

"I was raised in a medical family on the West Coast and was not really aware of the civil-rights groups and struggle. Not until I was 19 1/2 years old and traveled across the country and saw those (segregated) bathrooms, those four bathrooms, then it hit me," says Lax.

After that cross-country trip, Lax joined some political groups but largely pursued his career of photog-raphy and jewelry making. He had a jewelry business in Los Angeles and worked on advertising accounts for Mattel Toys and Frederick's of Holly-wood.

In 1967 Lax ended up in San Quentin for violation of parole from a bad check charge. There he says he experienced another kind of personal outrage. "I walked into San Quentin and it was 60 percent black, less than 1 percent of the administrators were black. And that was totally out of proportion to the state's population of 12.5 percent." He helped start a black awareness program and designed a cover of a prison program that became popular with the inmates, he says. The sketch gradually evolved into the jewelry.

After his release, Lax returned to buckles, rings and earrings, but says the Muntu idea became a passion. He started marketing a piece called the Afro-American in 1972 by taking out a full-page ad in Ebony. In six months, however, Lax and his wife went broke.

As the dust of curiosity about the black experience settled following the "Roots I" telecast, Lax decided the time was right to try to market Muntu again. To years ago, Sam and Carole Lax reopened their sales campaign with a press conference that featured. Los Angeles Mayor Tom Bradley and actor Louis Gossett. Gossett became Muntu's national spokesman. Lax went out on the road, pressing pins on author. Alex Haley and Ambassador Young. The promotion tour with Gosset failed and Lax turned to individual distributorships.

The jewelry caught the eye of Yvonne Price, director of the Leader-ship Conference on Civil Rights. "I sought Sam out after I saw the jewelry. Then I bought a couple of hundred pieces and sold them to friends. In the last two years she has become an adviser to Lax, visiting the work-shops in Los Angeles, and introducing him to leadership of black church ushers groups and black trade unionists. "I like the design because I am a person who has roots in America and roots in Africa. And I just believe in Lax."

Lax says the Muntu isn't an identity symbol. "It simply shows the world we all have one stem, scientifically we all come from Africa," says Lax. He relishes his own observation but his smile evaporates quickly. "The people in the jewelry business think I'm crazy. I know I can always go back to the other jewelry but right now I have a disease called Muntu."