Gold is worth almost twice as much as it was a year ago.

Real estate in some parts of Washington is selling for two and a half times what it cost in 1975. Cooper, coffee, sugar, corn and wheat prices are climbing despite abundant supplies.

Speculation has become standard operating procedure in the American economy -- people are buying things on borrowed money, betting that inflation will make them winners as prices climb.

Now the Federal Reserve Board's decision to restrict credit is threatening to pop the speculative bubbles, by cutting of the flow of money that fuels inflation.

Prices could fall -- or at least flatten out -- and speculators could fail. Even banks are threatened, and some could go under, warns John Heimann, the comptroller of the currency, who is in charge of bank regulation.

The collapse of a speculative bubble helped touch off the Great Depression, 50 years ago this month, in October 1929.

But in half a century, the United States has installed a number of protective devices in the nation's fiscal infrastructive to keep bursting bubbles from disrupting the economy in any wholesale way.

There is federal deposit insurance to protect bank customers, unemployment compensation to save the jobless, limits on borrowing for speculative investments to protect stock market investors and a regulatory bureauracy to protect "the little folks."

But for those who have chosen to play the speculator's game, there are dangerous times ahead. The government is not about to bail out the farmer who gambles his crop in the pits of the Chicago Board of Trade, or the real estate renegade out to make a painless million in the ghettoes of Washington.

Federal Reserve Chairman Paul Volcker made this clear in a speech Monday to the American Bankers Association convention in New Orleans.

"This is hardly the time to search out for new exotic lending areas or to finance speculative or purely financial activities that have little to do with the performance of the American econony," Volcker told the bankers.

The fed chief -- whose inflation fighting strategy has been cheered by the White House -- urged the bankers not to put up the money to finance speculative investment in the gold, foreign exchange and commodity markets where business is booming.

On New York's Commodity Exchange -- the nation's biggest gold market -- more than twice as many futures contracts for gold have been traded in the first nine months of this year as were traded last year. Gold trading is up 116 percent, total volume on the Comex is ahead by 76 percent and the combined business of the nation's 11 commodity exchanges is 25 percent greater than a year ago.

The figures mean that either many more people are in the commodity markets, or the same population of speculators is risking much more money on the rise and fall of commodity prices.

With increased speculation have come higher prices for most commodities, apparently because much of the new money in the markets has been invested by newcomers, convinced that prices are headed up.

In some cases speculative interest have pushed prices beyond levels professional traders consider realistic.

Take copper. It's now selling for 93.5 cents a pound -- up 11 cents since August and more than 20 cents in the past year. "The price is much higher than the fundamentals justify," contends Thomas Barrow, chairman of Kennecott Copper Corp., the nation's biggest producer.

"We're in the hands of a bunch of speculators," the Kennecott boss complained recently. "When that happens, you never know. . ."

The same thing has happened, many professional investors believe, in the Washington area's hottest speculative market -- real estate.

The prime rate now is at 14 1/2 percent and many real estate investment loans carry interest charges two points higher than that. In addition, most real estate investors have to pay one "point" -- one percent of the loan -- up front to the lender, raising the rate to 17 1/2 percent. On top of that many banks require borrowers to keep 20 percent of their loan as a "compensating balance" in a checking account. That pushes the actual interest rate past 20 percent.

"There's no way you can generate enough money [from renting a building] to justify that kind of expense," one lending specialist said this week. "They're gambling on inflation."

If the Federal Reserve succeeds in reducing the current annual inflation rate of 13.6 percent, the paper profits of speculation in real estate, or copper or corn could disappear.

If the speculators fail, so in some cases, will the banks that have loaned them money. That is one of the dangers Comptroller Heimann had in mind when he raised the possibility of bank failures. He warned bankers to assess the quality of their loans and to protect themselves from going down with their customers.

If the Federal Reserve succeeds in slowing the runaway inflation rate, the speculators who have been riding the whirlwind could see their paper profits blown away.