JOHANNESBURG, NOV. 26 -- The Anglo American Corp., South Africa's largest mining and industrial conglomerate, announced plans today to offer more than 250,000 employes -- mostly blacks -- paid shares in the corporation in an effort to demonstrate that a free market economy offers the greatest opportunity for growth and stability in the midst of political turmoil.

The De Beers Consolidated Mines Corp. simultaneously announced plans for a similar employe shareholding plan that would benefit up to 20,000 mostly black employes.

However, the black National Union of Mineworkers, underscoring the wide gulf that exists in South Africa between white management and black labor, immediately rejected the proposals as a "maneuver to ensure that free enterprise is entrenched in a postapartheid society."

"It amounts to political and economic blackmail," declared NUM Secretary General Cyril Ramaphosa, who in August led a crippling three-week strike against Anglo American and other major South African mining firms.

To end the strike, Anglo American, widely considered one of the most progressive employers in South Africa, fired nearly 40,000 miners, stunning the union and embittering many blacks.

Since then, the company announced plans to house thousands of black miners and their families near four gold mines, a decision that would enable large numbers of black miners to live with their wives and children for the first time in a century of South African mining.

Anglo American Chairman Gavin W.H. Relly told a news conference here today that the corporation initially will give five paid shares to its 2,600 headquarters employes with at least two years service.

The approximately 70 companies in the Anglo American chain have been asked to provide 250,000 qualifying employees with paid shares, the number of which will be determined by the individual companies, Anglo American executives said.

The shares to be allocated could be worth about $750 to each participating employe. The total cost of the shareholding plans to Anglo American and De Beers would be about $200 million.

Relly said the Anglo American plan was unrelated to the miners' strike and that preparation for it began about two years ago.

With $12.4 billion in assets and with earnings last year of $735 million, Anglo American accounts for 60 percent of the equity on the Johannesburg Stock Exchange. The company mines gold, diamonds, coal and other minerals, manufactures steel, chemicals, automobiles and other products and is involved in agribusiness, computer services, banking and insurance.

Anglo spends about $20 million a year on what it calls "social responsibility" programs, mostly community improvement projects and education of blacks. Additionally, it has pressed for reforms of South Africa's apartheid system of racial segregation, most recently urging repeal of the 1950 Group Areas Act, which strictly segregates residential areas by race.

Ramaphosa said his union had canvassed many of its nearly 300,000 members and that the consensus among them was that "the scheme stinks."

"This initiative is an attempt to undermine the strength of the unions. What the workers are demanding is that they get a living wage and a bigger share of the profits. . . . They won't be tricked into a paltry share-ownership scheme," Ramaphosa said.

Black miners in South Africa earn about $285 a month.

Anglo American's industrial relations consultant, Bobby Godsell, said the company did not consult the union on the shareholding plan because participation in it is an "individual decision."