How to buy a diamond without buying a story

Four things that matter, three that do not, and the one question to ask any jeweler.

Most people arrive on 47th Street braced for a fight. They have read that they will be pressured, upsold and outmatched on knowledge, and much of the time that is exactly what happens. It does not have to. Buying a diamond well comes down to four things that matter, three that mostly do not, and one question you should ask every jeweler you sit down with.

The four that matter. First, the certificate. A stone graded by the GIA, or the IGI for lab grown, has been described by someone with no stake in the sale. Read it, and make sure the number on the report is inscribed on the stone's girdle. Second, cut. It is the only one of the four Cs a person controls, and it is the one your eye responds to; a well cut stone a grade lower in color will outshine a poorly cut one a grade higher. Third, the stone under daylight. Fluorescence, milkiness and a warm tint only show at the window, never under a counter lamp. Fourth, the setting. A stone that is not held properly will not stay a stone you own.

The three that mostly do not. Clarity above VS2 is a laboratory distinction, not something you will ever see without a loupe. Color between D and G is the same story in a yellow gold setting. And the brand on the box, which is the most expensive thing about many rings and the least visible on the hand.

The question. Ask the jeweler to show you a stone one grade lower than the one they recommended, side by side, in daylight. A good jeweler will do it happily and tell you plainly whether you would see the difference. A jeweler who will not is telling you something too.

What we do differently is simple. Every stone we sell has been looked at under a loupe and by the window by the person who will sell it to you, before it went into the case. We carry the certificate to the counter and read it with you. And we will always show you the stone one grade down, because the ring you should buy is the one you will not regret in ten years, not the one that moves the most stock this month.

Come in on any day we are open. There is a chair, there is daylight, and there is as much time as you need.

Malidani has held the corner at 1200 6th Avenue, the entrance to 47th Street, since 1986.