More than a century after mining companies and prospectors were granted the right to buy federal lands for $5 an acre or less, Congress appears poised to suspend the sales.

As currently written, the Interior Department appropriations bill would suspend the land sales for one year while Congress considers major revisions to the so-called 1872 mining law, which governs the mining of "hard- rock" minerals such as gold and silver on federal lands. The measure has been approved by the House, and it cleared the Senate Appropriations Committee Tuesday.

The law allows mining companies and individuals to stake claims on federal lands, and, if they can prove the presence of a valuable mineral, buy the land for $2.50 or $5 an acre, depending on the type of claim. In 1989, the federal government sold 19,000 acres at those prices.

The suspension would be a significant setback to an industry that is trying to preserve the 118-year-old law in the face of mounting attacks from environmentalists and others. The industry maintains that the law is essential to the high-risk business of culling precious metals from the ground; critics call it a "giveaway" that hurts both taxpayers and the environment.

The key moment in the debate occurred Tuesday afternoon when the Senate Appropriations Committee followed the House lead and voted 17 to 10 to suspend the sales. "Since 1872, the U.S. has sold off acreage the size of the state of Connecticut for $2.50 an acre," argued Sen. Dale Bumpers (D-Ark.), who sponsored the measure. "You're supposed to be stewards of the public lands."

Bumpers overcame stiff opposition from Sen. James A. McClure (R-Idaho) and Sen. Harry Reid (D-Nev.), who defended the right of individuals and companies to "patent" mineralized claims. "The reason you want to have a patented claim is so the federal government will leave you alone," said Reid.

The mining industry contends that because hardrock minerals tend to be widely scattered and costly to recover, the right of "free access" is essential for this kind of mining to survive. Keith Knoblock, a lobbyist for the American Mining Congress, said that the patenting provision is particularly important because "the mining industry needs the security of tenure, which a patent provides, if we're going to compete in world markets."

But critics maintain that the right of mining companies to patent their claims limits federal oversight of the public lands. "Anytime {federal land managers} look at regulating a proposed mining operation, they are always conscious that if they regulate too stringently, the company will simply take the land and remove any federal control whatsoever," said Philip Hocker of the Mineral Policy Center.