Cleopatra, they say, was obsessed with emeralds. So much so that centuries later, people still called the ancient Egyptian mines "Cleopatra's mines." But the last pharaoh of the Ptolemaic dynasty was not the only one. Through the ages, emeralds passed through the hands of emperors, maharajas, aristocrats and some of the most elegant brides in the world - and piled up legends about love, fidelity and, oddly enough, infidelity along the way.

In the Middle Ages, people believed an emerald could predict the future, protect against curses and even reveal whether a lover was lying. The stone supposedly lost its colour or cracked when someone was unfaithful. An infidelity detector, long before phones and social media took over that job. The irony is that the very same stone later became the star of some of the greatest declarations of love of the last century.

A 167-carat wedding gift

In 1931, American tycoon Clarence Mackay chose an emerald for one of the most spectacular wedding gifts ever - for opera singer Anna Case. According to Francesca Cartier Brickell's book on the jewellery family, the house of Cartier made an Art Deco necklace with a 167.97-carat Colombian emerald at its centre, surrounded by 35 more emeralds and 2,191 diamonds. The necklace is now owned by the Smithsonian Institution, and its centre stone is the largest cut emerald in the collection.

Emeralds also feature in one of the most controversial love stories of the 20th century. Edward VIII gave Wallis Simpson small crosses that eventually formed a bracelet, again by Cartier, full of personal messages. Each cross marked a moment in their relationship, and one, made entirely of emeralds, commemorated their wedding in 1937. The nine-cross bracelet was sold at auction in 2010. A piece of jewellery that served as the secret diary of one couple - and of one abdication.

Emeralds have long drawn attention outside Europe too, especially in India. In 1926, the Maharaja of Kapurthala commissioned Cartier to make a turban ornament from emeralds, diamonds and pearls taken from his own treasury.

Jackie's ring

When John F. Kennedy and Jacqueline Bouvier announced their engagement in 1953, the ring was far from a classic solitaire. It was a Van Cleef & Arpels piece in the toi et moi style - "you and me" - in which two stones sit side by side on the same ring: a 2.88-carat diamond and a 2.84-carat emerald, set off by smaller stones. Interestingly, the ring was chosen at the Fifth Avenue boutique in New York not by the groom, but by his father, Joseph Kennedy.

Jackie made it her own anyway. In 1962 she replaced the elongated baguette diamonds with marquise-cut ones and created an almost botanical arrangement that is instantly recognisable today. At the time, colour barely existed in engagement rings, and her choice went on to inspire, decades later, the rings of stars a long way from the classic image of a first lady.

Cleopatra, take two

A few years later, Elizabeth Taylor and Richard Burton fell in love on the set of "Cleopatra," and jewellery quickly became their private language. For their engagement, Burton gave her a Bvlgari brooch with a 23.44-carat emerald that could also be worn as a pendant. Taylor wore it at their 1964 wedding, at the neckline of her unconventional yellow wedding dress. Other emeralds followed, among them a lavish necklace from the same Italian house.

It wasn't an engagement ring like Jackie's, but the story may be better: the actress who played Cleopatra ended up with the same passion for the same stone as the Egyptian queen. A stone that supposedly exposed liars ended up adorning the most famous marriages - some of which, as we know, did not last forever.