It is pleasing that from something as primitive as oil -- decayed prehistoric organic matter -- there now arises something as refined as a superb art collection. The Getty oil fortune has produced a jewel of a museum here and soon will produce another on a 742-acre hilltop in the Brentwood section of Los Angeles. In the process it is creating a fascinating exercise of statesmanship in the service of connoisseurship.

It is an exercise that, if performed imprudently, could convulse the art world and provoke "cultural protectionism." Performed judiciously, it will result in an art institution unrivaled anywhere.

J. Paul Getty had a lifelong passion for antiquities. As an American at Oxford in 1912, and later, he studied the classics in Latin and Greek and was an amateur but serious archaeologist. When he died in 1976 he stunned the art world by allocating to his avocation -- the collection of art treasures -- the fortune amassed in his vocation.

Harvard's endowment is $1.7 billion. The Getty Trust's is $2.4 billion, 10 times the endowment of New York's Metropolitan Museum. Federal law requires that such trusts spend a certain small percentage of their worth annually. The Getty's small percentage is approximately $100 million. Think of it: about $2 million a week. Last year, Washington's National Gallery spent $3.8 million on acquisitions, the Metropolitan $7 million.

The Getty can buy anything put up for sale. Because it can buy what it wants, it must be careful to want what it ought to want. Were it to throw its full weight around, it would skew the art market in two ways. Prices of art from prior to 1900 (the Getty's limit) would be distorted. And government would become even more active in producing art purchases, in the name of preventing the "pillaging" of national patrimonies.

The market for fine art is necessarily peculiar. The value of the objects has nothing to do with the costs of labor and material. The supply is small and fixed. Demand is a function of such disparate and often nonrational factors as fear of inflation, conspicuous consumption, institutional competition, a true passion for art and, increasingly, defensive nationalism.

At a recent Sotheby's sale of Impressionists, there were an estimated 40 people each worth more than $100 million. In 1985, 35 paintings and drawings were auctioned for more than $1 million each. Three of the top four went to private collectors. Getty paid the top price, $9.6 million, for an Italian renaissance masterpiece. It has stayed in Britain while British sources try to match the price, as British law allows.

Britain is exceptionally liberal in allowing the export of art. Cultural nationalism is understandable and, up to a point, admirable. But at some point it collides with the raison d'.etre of museums, which exist to share and nurture the civilization that unifies the civilized nations.

The Getty Museum's director, John Walsh, is by choice a scholar and of necessity a diplomat. Last year his museum bought the Ludwig collection of 144 illuminated manuscripts, and that single purchase made its collection one of the top three, behind the Morgan Library's and even with the Walters Art Gallery in Baltimore.

Photography is the one (and deplorable) exception to the Getty's concentration on art from before 1900. It recently began its photography collection by buying nine of the most desirable private collections.

But in 1983 the Getty, although eager to acquire the 12th-century Gospel of Henry the Lion, backed away in favor of German interests who considered it a national treasure.

Last year in Britain, Getty purchased six Old Masters drawings for $9 million. The Getty was interested in three dozen of the 70 drawings for sale and seriously desired 12, but decided the price -- in money and goodwill -- was too high in most cases.

Fortunately, the Getty is not required to spend the $100 million on art objects. Museums exist not only to collect but to conserve, exhibit and elucidate. The Getty has ambitious plans in all four areas. It has the fastest growing library -- 50,000 volumes a year -- in the world. It will stress the neged science of art conservation and restoration. It will support serious art curricula for primary and secondary schools where philistine conservatism has dismissed art as a frill unrelated to economic growth.

Los Angeles has more than its share of cultured despisers who feel adequate only when condescending to others: "The difference between Los Angeles and yogurt is that yogurt has an active living culture." Ten years from now Los Angeles will be laughing last, and best. The statesmanship of the Getty Trust will have given the city a cultural ornament unrivaled in any metropolis.