A golden age this is not -- it is, however, an age of gold.

According to Saloman Brothers' latest index showing the performance of 15 tangible and financial assets, the price of the glittery metal increased 104 percent in the year ending June 1, 1980.

Petroleum -- "liquid gold" -- proved almost as good an investment, rising 92.4 percent. Bonds, which had a negative return of 3.2 percent, languished at the bottom of the index.

"It seems clear that the confrontation between tangible and financial assets still is being won decisively by tangibles," declared Robert S. Salomon Jr., a general partner in the New York brokerage firm. Its 10-year index indicates gold, oil and bonds occupied the same relative positions a decade ago although the differences in returns were not so wide.

This is the fourth consecutive year that Salomon Brothers has published its index for the increasing numbers of individual and institutional investors interested in holding real goods -- or certificates of ownership -- as hedges against inflation.

Those objects or commodities ranked on rate of return are, in addition to gold and oil, Chinese ceramics, stamps, rare books, silver coins, Old Master paintings, diamonds, farm land and housing. The financial assets are stocks, bonds and foreign currencies.

Gold's brilliant performance resulted from a 104 percent price rise from $274.60 a troy ounce on June 1, 1979 to $535.50 a year later, although between those dates gold threatened to break the $1,000-an-ounce barrier.

During the previous year, gold was merely the third best investment one could make. Oil gushed into second place from 12th a year ago as the cost per barrel soared to $28. (Salomon Brothers had previously used the U.S. government's price of crude at the well head for its index, but switched this year to what the firm considers a more accurate indicator, Saudi Arabian light crude.)

On Salomon Brothers' 10-year index, gold and oil showed an identical compound annual rate of return of 31.6 percent. Dismissing theories that link the prices of the two commodities, Robert Salomon called it a coincidence and added the company would be reluctant to read anything into this as far as future linkage of gold and oil prices is concerned.

Despite its more than one brief shining moment in the headlines this year, silver wound up in third place, down from top investment of the year in 1978-79 when it racked up a 62.5 percent gain. Like gold, silver also took a roller coaster ride this year, up to $50 an ounce and back before settling at $13.55 on June 1, 1980. Twelve months before, silver was selling at just $8.60 an ounce.

All other tangibles paled before these precious metals and oil. Rare stamps appreciated 43.2 percent, less than the 60.9 percent they went up the previous year.

The price of U.S. coins and diamonds increased by approximately the same amount, 25 percent, a hefty rise over the previous year when their prices grew by just 10 and 4 percent respectively. (The diamond index is based on DeBeers wholesale prices for all grades and sizes. Therefore, the appreciation is considerably less than that of investment grade diamonds, the measure used by brokers and dealers.) The value of Old Master paintings jumped 17.4 percent, compared to 15.2 percent in 1978-79.

Chinese ceramics, a hot investment last year with a 31 percent gain, cooled off to a mere 13 percent gain last year. As such, they did not even keep up with the cost of living, which hit 14.5 percent in June.

Neither did housing and farm land. Housing went up but 10.4 percent last year, compared to 13.7 percent during 1978-79. Farm land, which had proved such a good investment when inflation was 10.5 percent, no longer kept pace last year, even though the return on investment remained at the same level, 14.2 percent.

Those investments that outpaced inflation in each of the two years were gold, silver, stamps and Old Masters. Those that ran behind both years were rare books and all the financial asssets.