Emerald

Emerald is the green variety of the mineral beryl, coloured by traces of chromium and vanadium. Those elements rarely meet the beryllium that beryl needs, which is why fine emeralds form in so few places on earth and why they have been treasured for thousands of years.

It is the birthstone for May, and its colour has stood for renewal and new beginnings in many cultures.

An emerald is judged above all on its colour. The most prized stones are a pure, vivid green to slightly bluish green, neither too light nor too dark, with the colour spread evenly through the stone. A vivid stone with visible inclusions is worth more than a cleaner one with pale or greyish colour.

Colombian emeralds are famous for a warm, intense green. Zambian stones tend towards a cooler, slightly bluer green. Brazil, where the story of Bairro Jabour began, produces emeralds of bright, lively colour, often with good clarity.

Almost every natural emerald has visible inclusions. The French call them the jardin, the garden, because they can look like moss or foliage inside the stone. They are an accepted part of emerald’s character, and a truly clean natural emerald of good size is extraordinarily rare.

What matters is that the inclusions do not cloud the stone or sit where they weaken it. Look for an emerald that is bright and transparent, with life in it, rather than one that is flawless.

Most emeralds are treated with oil or resin to fill tiny surface-reaching fissures and make them less visible. Oiling, traditionally with cedarwood oil, has been practised for centuries and is accepted across the trade. Laboratories report the degree of enhancement, from none or minor up to significant.

Minor enhancement is normal. The less enhancement a stone needs, the more it is generally valued. What matters most is disclosure: a reputable report should state whether and how much the stone has been treated.

Emerald is hard enough to resist scratches in daily life, but its natural inclusions make it more brittle than sapphire, ruby or diamond. A sharp knock can chip it. That does not rule it out for an engagement ring: it means choosing the setting with care.

The emerald cut was developed for this stone. Its cut corners remove the fragile points. A bezel, or claws that protect the corners, add security, and a slightly lower setting keeps the stone out of harm’s way. Take it off for the gym, gardening and heavy work.

Clean it with warm water, a drop of neutral soap and a soft brush, then rinse and dry with a soft cloth. Never put a gemstone in an ultrasonic cleaner or a steamer.

Heat, steam, ultrasonic vibration and harsh chemicals can all affect the oils or resins in a treated emerald and the stone itself. If an emerald begins to look dull or shows more of its inclusions over the years, a jeweller can assess it and arrange re-oiling.