The four Cs -- within our context here -- do not refer to an old doo-wop group. In diamondology, they refer to a stone's character. We'll list the three easier Cs -- carat, cut and color -- and you do your part: Give us that fourth little devil:

Clarity.

Cupidity.

Continuity.

Counting down the other Cs -- when it comes to color, a purely and perfectly white diamond is the most valuable and expensive. Correct?

Even though I sense a trick question here, the answer is so patently ''yes,'' I'm goin' for it.

Ain't necessarily so.

Onward now to carats, quiz-lovers. If you find a 50-point diamond under your pillow tomorrow morning, what will you have (besides quite a shock)?

A 500-carat diamond.

A five-carat diamond.

A one-half carat diamond.

Let's cut to the cut -- and, please, if you will, size up for us the most popular shape:

Round.

Marquise.

Heart.

Now that we've run through the four Cs -- let's crown our knowledge with the most overarching C of all -- the fifth C (no relation to the fifth Beatle): Cost. How many clams does this average engagement ring cause us to cough up, we crassly inquire.

Almost exactly $3,000.

Close to $2,000.

$1,200.

All things being equal -- i.e., same quality characteristics are in place -- a two-carat diamond will cost twice as much as a one-carat diamond. Are we right, or what?

I'm going with ''what.''

I vote with ''right.''

Whether buying -- or, just as important, seeking an appraisal -- it's important to go to a jewelry professional you can trust. Nothing controversial there. Problem is, all you've got in your neck of the woods is a Dirty Don's Diamond Den and, of course cross-town, the bright lights of Parolee Paul's Diamond Palace. Where best to turn for a reputable referral?

Diamonds R Us Info, Serving the Nation Since… What Time is it Now?

The American Gem Society.

Someone whose jewelry and taste you admire.

Diamonds, of course, aren't just for the dainty digits of the affianced, the pinkies of dapper gents, or the tony ties of the tastefully tacked. They're also the birthstone for this month:

June.

April.

December.

Well, whether for engagement rings, pinky rings, birthstones -- or tiaras, for that matter -- how much would you say the annual retail market for diamonds in the U.S. totals?

Over $22 billion.

About $15 billion.

Just under $2.2 billion.

Ah, speaking about totals in diamond sales -- here's a gal who personally -- or, perhaps more specifically and accurately, via her doting hubbies -- has kept the diamond market brisk and healthy over the years: the glamorous and glittering Elizabeth Taylor. The 69.42-carat pear-shaped Taylor-Burton diamond (not to be confused with her equally famous 33.19-carat Krupp diamond) was put to alternate use, when La Liz decided it was just too darn big to be worn on a ring. So how did she use it? As a:

Paperweight.

Lethal weapon, when crooks broke into her L.A. mansion.

Pendant on a necklace.