2.06 ctw Emerald & Diamond Tennis Necklace – 18k Yellow Gold, 15–17 in

18k yellow gold. Emeralds, 1.53 ctw. Diamonds, 0.53 ctw. Total length 17 inches, adjustable at 15 and 16 inches.

The hard part of an emerald line necklace is not the emeralds. It is making them agree.

Emerald is beryl colored by chromium or vanadium, and its green varies enormously — by deposit, by mine, sometimes within a single crystal. Set one large emerald and variation is character. Set a row of them and any stone that runs bluer, greyer or paler than its neighbors announces itself immediately. The eye is extremely good at catching a break in a repeated line. Matching a tennis run of emeralds is slow, expensive work, and it is most of what you are paying for here.

Yellow gold is the traditional choice for emerald and the correct one. Green and gold are neighbors in warmth; the metal lifts the green rather than cooling it. In white metal, emerald can read flat and slightly grey.

The diamonds are doing structural work as much as decorative. Green absorbs light; a continuous row of emerald alone would read heavy. The 0.53 carats of white break it up and keep the line moving.

On the adjustable length

Seventeen inches with rings at fifteen and sixteen is more useful than it sounds. Fifteen sits high on the throat and works with a high neckline or a turtleneck. Seventeen sits at the collarbone and layers under a longer chain. One necklace covering three positions is unusual at this level and worth knowing about before you buy a second.

Care

Nearly all emeralds are oil- or resin-treated to fill surface-reaching fissures. This is standard and disclosed, but it means no ultrasonic cleaner, no steam, no hot water. Warm soapy water and a soft brush, and store it flat and separate.