Among reminders on buying jewelry:

* For a good visual measure of the difference in quality of pearls, lay them on white tissue paper. "The customer can invariably pick up the strand that is the best quality," says Louise White of Dikomey Jewelers. "Look for luster and for something that doesn't have too many blemishes."

* Cubic zirconia (cz), simulated diamond, is considerably heavier than diamond. Find out whether the carat of cz you're buying is actually the weight of the cubic zirconia or whether the cz is the size of the carat diamond. A carat of cz will look about half the size of a diamond the same weight.

* Federal Trade Commission staff attorney Suzanne Patch, who handles complaints about the jewelry industry, warns mail-order consumers buying inexpensive unset stones by mail: "The price of setting those stones will be quite expensive, even though the stone itself may be inexpensive."

* Watch for the word "faux." "It started out applied to pearls and now it's being used everywhere," says Patch. "I don't think that all consumers, by any means, know that that's the French word for fake."

* Remember that just because it cuts glass doesn't necessarily mean it's a diamond. Diamonds do cut glass, but so do other things, such as quartz, some garnets, sapphires, rubies and cubic zirconia. "Glass is very soft," says one jeweler.

* Gemologist and lecturer Christine Krieger Brooks recommends looking at stones through a 10-power magnification microscope instead of the more common, smaller jeweler's loupe.

"Go to the museums," says Brooks, "to the finest first and work your way down."

When she was working at a retail store, a young couple came in and said they had $2,000 to spend on an engagement ring.

"They could get something today that two weeks from now they wouldn't be sure about. I said, 'Do me a favor, go to the museums and look, look, look. Train your eye to what's out there.'

"My boss was ready to kill me," 'What do you mean? That was a buying customer!' Well, they came back two weeks later and bought a $3,000 ruby-and-diamond ring because they were pleased that I didn't push them, that I wanted them to be educated."