Gold prices plummeted $27 an ounce today to $623,50, in part, traders said, because of an apparent easing of tensions between the United States and Iran over the hostages.

But several analysts said today's decline was merely the quickening of movement that has been long in the making.

At the same time that physical demand for gold remains low -- because of high prices, jewelry makers will use between 60 percent and 70 percent less gold this year than last -- large supplies of gold came of the market from the Soviet Union and the Middle East.

"There is just no absorption of the physical metal," according to Charles Stahl, editor of Green's Commodity Market Comments. "It has taken the markets a long time to realize this."

Although international developments usually affect the price of gold -- sometimes illogically -- Stahl scoffs at the gold investors who blame the decline on reasons other than a growing oversupply.

According to customs reports from Switzland, the Soviet Union shipped more than 807,000 ounces of gold to Zurich in September, by far the biggest Soviet sale in at least a year, according to James E. Sinclair, who heads the metals trading firm of Sinclair & Co. Sinclair said the Soviets often place large quantities of gold -- a major source of their foreign exchange -- directly in the Middle East.

But Sinclair said that with no Middle East demand for the metal (there are reports that Iran and perhaps Iraq are selling gold to finance their war efforts), the North American and European markets have been buying the metal. However, he said, those investors are now saturated, and the "complications" of the rumored hostage accord have pushed the price down faster.

Normally during periods of international tension such as the Iran-Iraq war, the price of gold would be expected to rise. It skyrocketed to record levels, for example, during the Soviet invasion of Afghanistan last January.

The reduction of world oil supplies by 3.8 million barrels a day should have triggered concern about oil prices and inflation and moved many investors to hoard gold. However, Sinclair said, Middle East investors recognize that oil demand in the United States will not grow sharply because high interest rates will impede recovery, and European demand may fall because of a growing econmic slowdown there.

In any event, today's $27-an-ounce decline was the continuation of a trend that began several weeks ago. On Oct. 10, the price of gold closed at $686.70 in New York. It dropped steadily last week, losing more than $31 an ounce. After regaining $2.80 on Monday and Tuesday, it dropped $7.50 on Wednesday, following the first rumors of a breakthrough in the hostage situation.

Some analysts linked the Soviets' sale to that nation's need for hard currency to buy grain supplies. But Stahl said that the sale -- which netted the USSR between $500 million and $550 million -- more likely occurred because the Soviets recognized the price was a favorable as it would be for some time to come. Sinclair's experts estimate the sales occurred between $670 and $700 an ounce.

Stahl said a further indication of the excess supply of gold is the huge influx of the metal into warehouses apporoved by the Commodity Exchange in New York, the nation's major gold trading floor. He said that investors, unable to unload the gold, instead are selling futures contracts and delivering the gold against those contracts. Comex gold stocks rose more than a million ounces to a record 4.3 million ounces in September.

Both Stahl and Sinclair forecast a protracted decline in the price of gold -- which was the trading rage among both small and large investors last year and early this year.

Stahl said there will be a "technical rally" in the next few days as disbelievers buy at the seemingly cheap price, "but the rally will not hold."

"There are definite signs that this is a tired market," said Sinclair. "I only look at the hugh number of ads in financial publications advising that now is the time to buy gold. When that happens, it is time to sell. The time to buy is when there are no ads."