Why blacks trek to South Africa for $47-a-week jobs

* Richard, a lanky young black from Lesotho, earns more in a week working in a South African gold mine than he would in a month tarring roads in his native country.

* Albino's wife and nine children in Mozambique would have less to eat if he did not send them weekly parcels of corn and peanuts from South Africa, paid for with mining wages.

These men choose to work in South Africa, yet they are constantly homesick. As migrant mine laborers, their contracts call for 10 months of continuous work before a four-month visit ''home.''

Such are the trade-offs for the more than 500,000 migrant workers who leave families in and outside South Africa to work in this country's mines. The work is strenuous, the living conditions spartan, and the chances for advancement for blacks limited by entrenched discriminatory job practices.

Critics call the migrant labor system exploitative. Proponents point to the economic benefits.

South Africa's use of migrant miners, many of whom are foreigners, is a locomotive for development in southern Africa. It pumps a large sum of money into the poor rural areas of South Africa and its neighboring black states. Black miners send home an estimated $300 million (US) a year.

However good or bad the migrant ''system,'' the workers themselves are eager for the jobs.

''Everyone wants to come here,'' says an elderly man from Botswana who first went to work in a South African mine in 1935 and has since been joined by his two sons.

Richard from Lesotho illustrates the initiative it takes today to get a job on a mine. When he went to the recruitment office in his small nation's capital of Maseru, it was clogged with hundreds of applicants.

So Richard journeyed to the Blyvoor-uitzicht Gold Mine near Johannesburg. His eagerness so impressed the mine management that they gave him a letter of recommendation, which sped him to the front of the queue back in Maseru.

The picture of eager job-seekers is the same throughout southern Africa, says Tony Fleischer of The Employment Bureau of Africa. TEBA recruits mining labor through 160 offices sprinkled over the subcontinent.

For the most part the laborers come from rural areas where jobs are few and wages low. Relatively speaking, work in a South African mine is far better than anything available on the local job market.

As a result, labor supply far exceeds demand. Mr. Fleischer says that in the hard rock mining sector, where migrant labor is most heavily used, the number of migrants seeking jobs is about double the number of mine positions available.

This oversupply is one reason critics of the migrant labor system say mines have been able to exploit workers. Also, because of the transitory nature of the migrant labor force, they have remained unorganized and effectively subject to whatever wages and living conditions the mining houses impose.

International labor organizations have called on black African states to withdraw labor from South Africa. Zimbabwe did so last year, ending TEBA's labor recruiting in that country because it considered it exploitative.

But with the generally weak economies of southern Africa and their rising populations, the demand for jobs in South African mines is not expected to abate. If anything, South Africa, not its neighbors, may be the one that turns away its foreign job-seekers.

After a few years of rapid expansion, gold mines, which employ the greatest number of migrant blacks, are shelving new projects until the gold price increases.

With rising unemployment in South Africa itself, particularly in the rural ''homelands,'' there may be political pressure to hire more miners from the local market and fewer from neighboring countries.

To some extent, this sort of shift has already begun. In 1974 nearly 80 percent of TEBA recruits were foreign citizens, compared to 40 percent today.

Mr. Fleischer expects the share of workers coming from nearby states will continue to decline.

One reason is that mining jobs, long shunned by South African blacks, are growing more attractive. Wages and living conditions are improving. Wages in gold mines, for example, have risen 267 percent faster than inflation in the past decade.

Although improvements are noticeable, a black miner's life style in South Africa remains one of few comforts. Home is a stark hostel, similar in many ways to an army barrack. The miners' belongings usually are blankets and a foam cushion, which becomes a bed on a concrete slab or metal bunk, and a small metal locker.

Food, medical care, shelter, and recreation are all provided. Miners earn an average wage of $47 (US) per week.

One of the most criticized aspects of mining is that it still contains some of South Africa's most discriminatory labor practices.

The small but powerful white mine workers unions have managed through labor agreements and legislation to protect their positions in the mines at the expense of blacks.

The central reform that has already been recommended by a government-appointed labor commission is the granting of certain job certificates to qualified blacks, who at present are excluded from holding them. The certificates are necessary before a mineworker can advance to a number of higher job positions.

Although the South African government has accepted this reform ''in principle ,'' it has left it to the white unions and mining houses to resolve. It has called for the change within a ''reasonable period of time,'' but the mining industry has not yet pressed the issue with the unions.