The hottest commodity in the world last week was not gold, silver or diamonds, but a piece of paper, colored green: The American dollar smashed all records, shriveling the value of other currencies. Huge sums of money poured into the country seeking high-interest returns in government securities or a high profit through purchases of American companies.

The extraordinarily high value of the dollar has acted as an enormous catalyst to exports from other countries to the United States. From mid-June 1980 to mid-June this year, the dollar appreciated 58 percent against the mark, 44 percent against the Swiss franc, a whopping 109 percent against the French franc and 9 percent against the yen (30 percent, taking a 1979 base).

At the close of the week, it took a record 9.115 francs or 2.9688 West German marks to buy one dollar. The British pound slumped to a new low of $1.2785. Traders talk of the possibility of 10 francs or 3 marks to the dollar -- even of parity between the pound and dollar, although that looks less likely.

The big jumps already scored by the dollar put American exporters at a great competitive disadvantage. They are one of the main explanations for the huge American trade deficit -- the mirror image of which are trade surpluses in Europe, Japan and elsewhere.

Yet, just a little more than four years ago, the dollar was teetering on the brink, and Europeans were screaming "benign neglect" because the weak dollar was pushing American goods into their markets.

Gold soared during that period to a record-breaking $850 an ounce (Jan. 21, 1980). But last week, while investors were plunging into dollar investments instead of gold, the once-precious metal edged below $340 an ounce.

As the authoritative Green's Commodity Market letter notes, Rep. Jack Kemp's call at the Republican National Convention to "make the dollar 'as good as gold' sounds like a joke, considering that over the last four years the dollar has been better than gold."

But the nagging question, and one that baffles the experts, is: How long can the dollar continue at its peaks in the face of enormous deficits in the international trade account and in the current account, which includes the balance in services as well as merchandise?

C. Fred Bergsten, who was an assistant Treasury secretary in the Carter administration, admits that he had expected the dollar to turn down before this, "but at the moment, it's hard to know what will turn it around, barring some pick-up in economic performance in Europe, or a decline in interest rates here."

Most of the experts had warned that, as the American federal budget deficit worsened -- with no signs that the Reagan administration and Congress would tackle it -- Europeans who had been investing heavily here to benefit from high interest rates would start to hold back.

But in fact, what appears to be happening instead is that European and Japanese investors, convinced that the American economy will continue to grow at a faster rate than their own economies -- with bigger profit margins -- keep pouring the money in.

International experts Otmar Emminger and Edward M. Bernstein argued in separate analyses that the record inflow of capital is the driving force behind the record dollar rates.

It reverses the pattern that French journalist Jean-Jacques Servan-Schreiber feared back in the late 1960s, when he wrote in his famous book, "The American Challenge," that American investment would overtake and overpower Europe. Now, net European investment here exceeds American investment there.

Emile van Lennep, who is retiring next month as head of the Organization for Economic Cooperation and Development, said here the other day that so long as European and Japanese investors can make handsome profits out of investments here, the flow of capital is likely to continue, even if interest rates come down.

But the conventional wisdom is that the pace of foreign investment here is probably unsustainable, and that the dollar eventually will come off its high -- preferably slowly, but possibly in a dangerous collapse.

"The longer the disequilibrium lasts, the more fragile the present exchange rate structure becomes," Emminger said recently. "Nobody is in a position to foresee whether an eventual correction of the exchange rate will come gradually, with a 'soft landing,' or whether there will be an abrupt change."

But what will bring the dollar down? Most economists have said that a willingness to reduce the budget deficit by raising taxes will result in lower interest rates, automatically cutting the dollar's exchange rate. This is what this year's International Monetary Fund "World Economic Outlook" said would be "the single most beneficial change in the world economy."

But will lower interest rates automatically bring the dollar down? The textbooks of 10 and 20 years ago would have said, "For sure!" In today's environment, who can tell?

"For the exchange rate to change, things have to look worse here and better in Europe and Latin America," says Morgan Guaranty economist Rimmer de Vries. "I don't see that happening for a number of years."

The growth of the U.S. economy so sharply surpasses the pace anywhere else in the world that lower interest rates arising out of a modest deficit reduction are likely to be taken as one more reason to pour investment money into this country's markets and factories. Thus, the dollar could defy the experts and stay close to its stratospheric level for a long time, even if interest rates decline.