Emerald asks more of a jeweller than any other stone in regular use. It is comparatively soft, and almost every natural emerald contains internal fractures, known in the trade as the jardin, which are accepted as part of the stone rather than treated as flaws. Setting one securely without stressing it is skilled bench work, and it is the sort of job our Hatton Garden workshop takes on regularly.This collection includes Charlotte, Fulham, Kasama, Olivia, Sophia and Windsor, covering solitaire, trilogy and cluster arrangements.Colour is what determines an emerald’s value, far more than clarity. The most sought after stones are a saturated bluish green, and Colombian material is generally considered the benchmark, though Zambian emeralds have gained ground for their depth of colour. Almost all emeralds on the market are oiled to improve appearance, which is standard practice and disclosed, but it does mean the stone should never go near an ultrasonic cleaner.Emerald is the May birthstone and marks the twentieth and thirty fifth anniversaries. If you are considering one for an engagement ring, it can be done well, but the setting needs to protect the stone and the wearer needs to know how to look after it. Our buyer guide to emeralds covers origin, oiling and care, and gemstone guides sets emerald alongside sapphire and ruby.