SOME AUTHORITIES say that fair young women are the best seekers of yu (jade). They take off their clothes and, nude, wade into the stream to seek the precious stones. Jade is yang or a male object. Woman is yin. Yang and yin yearn for each other. So in the natural way of things, woman and jade should come together in the moonlight.

To find jade, the women must wait for that warm quiet autumn night, when the world seems so still you wonder if it yet revolves. They look for a river with soft, sensuous sandy banks, easing down to the water. The women seek it not in the terrible torrent where the treasures of the deep earth are gorged up from the dark of the underground. The searchers instead choose a place where the full moon admires its face in the smooth waters of a depthless dark pool.

The moonlight shines on the jade, setting it apart from the ordinary stones of the river. The jade reflects back at the moon, its own light made more luminous by the moon.

These jade-finding techniques were explained in Tien kung k'ai, first Jade.") The author goes on to say, perhaps with less authority, that when buried in the mountain, jade is soft, like cotton, hardening as the water and air wash it.

The other day, Julia Murray -- fully clothed -- stood in the study room at the Freer, looking through the jades to select 130 pieces for an exhibit of ancient (third millennium B.C., through third century A.D.) Chinese jade scheduled Sept. 4 through February at the Freer Gallery of Art, that great treasure house on the Mall.

The word yu, means many things in China. As Hansford points out it is used in much the same way we use gold in English -- to glorify -- as in "golden boy" or "golden era." Often the term was used for a large range of stones, including jasper.

The term jade correctly is limited to two types of hardstones: nephrite and jadite. The ancient Chinese only knew nephrite, imported on boats and ox-carts at much travail from the Khotan and Yarkand riverbeds in the northwest Sinkiang, and perhaps from Lake Baikal in eastern Siberia. Jadeite, whose green-to-white colors are more familiar now, wasn't imported into China until the 18th century.

Nephrite is a magnificent stone of many colors, depending on the iron, chromium and manganese mineral impurities that have insinuated themselves into its formation. The purer jade is pale and translucent. In the great discs, called pi, in the Freer show, some are black-and-white marbelized, others are brown, beige to tan. On Mohs' scale of hardness with diamonds at 10, and talc at 1, nephrite is 6.5.

Looking at one espcially lovely piece, all browns melding into a rich red, you might think that the Chinese invented ceramics in an effort to match the nature-made material.

More than 4,000 years ago, in the prehistoric Neolithic or New Stone Age, the patient craftsworker sat by the river, working the precious yu as an act of worship. He (or indeed she) would select a slab of jade, perhaps found in the stream, or quarried. The slab might still bear the deep scars of the ax.

The worker would grind wet quartz sand into the jade with a wood, bone or bamboo drill or saw. Then, the craftsworker would rub it with sand to smooth out all the irregularities until the stone became as smooth as the surface of the dark pool where it had hidden.

Many of the pieces have a hole cut either at one end or in the center. No one knows whether the hole was for ornament or utility. But it must have been important to go to all the trouble to cut it. The worker would wet a stick of bamboo and roll it in quartz sand, then twirl it against the hard jade. A chisel from the late Shang dynasty (1200-1100 BC) still has the points of the bamboo captured in the holes.

Hours and hours would go by before the first dent in the surface would appear, because quartz is but a half a point harder than jade. The hole, when it was finally made, was conical, because the bamboo wore away as it cut into the jade, getting smaller and smaller toward the end. In some you can see the ridge, where bamboo being worked on each side met.

The Freer's jades live in beautiful dark cabinets with numbers shadowed in red and gold to make them stand out. The pulls on the cabinets end in a curious, almost star shape. The cabinets were made for Charles Freer, the founder of the gallery, and he kept his treasures in them in his home.

Murray rubbed a piece of jade and said, "It feels so good. You know, in some places, people wear jade just for the pleasure of caressing it. It has such a warm, human feel."

She laid the pieces out on a beige cotton cloth on several tables, sorting out the different kinds as she went, and describing their probable use. Later, Thomas Lawton, the director of the Freer and a great Chinese scholar, came down to point out his favorite jade beauties, and speculate on the mysteries.

The objects found in Neolithic sites in east and southeast coastal China fall into several categories. It's easy enough to explain those objects that clearly come from the utilitarian stone tools used during the Neolithic period: ax, adz, hu (trapezoidal harvesting knife), and chisel kuei. But some of the others are not so simple.

Pi, disk shapes, Murray explained, the "Rituals of Chou" were described as being for the worship of heaven. Another ancient shape, a squared cylinder, called tsung was supposed to be for the worship of heaven. But since Chou was written centuries later, these may be fanciful anachronisms. The other forms are hollow circles in several sizes, called huan (rings), yuan (bracelets), huang (semicircular ornaments), ping (handles) and animal shapes, undoubtably amulets.

"In the Shang dynasty (c. 1523-1028 BC)," writes Murray in an informative brochure with the show, "the jade repertoire was augmented by shapes based on bronze prototypes like spearheads and dagger axes (ko ). The scepter-like blade, chang, and the squared cylinder called tsung also rose to prominence in the late Shang, although their origins may actually be Neolithic.

One pi disk is covered with a relief ornamentation sometimes called nipples. Murray thinks of them as spirals. Actually on this particular piece from the Warring States period (fifth-third century BC, Chin-ts'un) the knobs are connected by a line giving them almost the look of small eye glasses.

Mask designs with starring bug eyes seem to have a kinship with the spirals. A tsung cylinder (c. 2000 BC) is especially intimidating. Another bulging bug-eyed moster, made up of incised lines and knobs is cut into a pendant. Some smaller undecorated pendants were probably part of a necklace, according to Lawton.

Murray notes that the surface decorations from the jades of the Chinese Bronze Age are similar to those found on bronze objects, but simplified: incised lines, thread relief or pairs of parallel incised lines making a single raised line.

Not many of the articles have inscriptions, perhaps because of the difficult work of cutting them. But a ko blade from the early Shang dynasty has a inscription painfully cut into it later, during the Western Chou period:

"On the Pingi-Yin day of the sixth month the king was in Feng. He ordered the Grand Guardian to inspect the southern states, to follow the Han [river] and go to guard the South. He ordered Marquis X to supervise the use of sheaves [of arrows], seven strings of cries [money] and 100 foot-soldiers."

Dragons in frightening forms rear their heads during the Western Chou (pronounced "jo") period but are simplified to abstract patterns during the next period called Eastern Chou (770-256 BC).

Lawton picked up a marvelous belt hood with a dragon head, a bumpy stomach and a scrolled side. "In tombs," he said, "these hooks sometimes are found across the chest as well as at the waist. The Chinese probably began to use such hooks after going into battle with the nomads from the north. They couldn't very well fight and ride while holding their clothes together."

One of the hooks that Lawton likes is made of perhaps iron, gilded and inlaid with jade. The more highly decorated ones come from the end of the Warring States and Early Western Han period (third-first century BC).

In the same case are two handsome jade vessels -- one a cup described as "winged" because of the shape of its two handles, the other a heart-shaped bowl with a pouring lip.

Lawton, who's writing a book and planning an exhibit on the Warring States period, noted that some of the most exquisitely made jade ornaments are from the Warring States period of the late Eastern Chou. "They were collected by Bishop William White in Yang, Honan Province, during the 1920s. He wasn't allowed to go see the tomb, but bought them from grave robbers. So we have little information on their position in the tombs."

The ornaments were used by the Chinese in life and death. A pair of combs has an elaborate scroll cutwork. Lawton says the combs may have been stuck in the hair for decoration as well as used for combing. A fearsome animal pendant described as a tiger looks a lot more like a rhinoceros. It has a curling tail and a tongue to match its body bumps. For some unexplained reason, it also has an incised bird marching up what may be its front leg.

A streamlined panther crouches on a handle. And a stylized dragon, looking rather coy, was likely a pendant. Two other pendants have dragon heads at each end of a half-circle. A scabbard ornament is made of raised and cut out spirals. Lawton explained that the Chinese always mounted dragons and other designs for belt loops and swords and such so they were right-side-up if the wearer looked down on them.

The most elaborate piece is a pectoral made of jade and gold. The necklace was designed to have pendants hanging both front and back to hold it in place. The woven gold chain has knobs where it crosses the shoulders. On one side hangs a pair of twin dancing ladies, carved, Lawton pointed out, both back and front. On the other is an elaborate ensemble of three pieces, each with dragon heads and scrolls.

There's even a small ring, intended for the bow finger, and another ring pierced to perhaps hang from the ear.

The great antiquity of the objects and the enormous skill of these ancient craftsmen make an awesome three-dimensional history of the Chinese people.