In her preface, Finlay says that she started thinking about jewels while researching her book Colour, which came out some years ago to considerable acclaim. Then she tells us that she was given an engagement ring composed of three fragments of mosaic from the Hagia Sophia which, though not in themselves jewels, have something of their precious status because of their special origin. Already the book is defined as both a professional and a highly personal enterprise. You can imagine the proposal: a sequence of chapters centred on different gems, explaining where they are to be found, offering a few historical anecdotes and stories associated with them, culminating in diamonds, the most fabled stone of all. But what could never have come across among the bullet points is the author’s zeal. She has obviously found it a thrilling and fascinating book to write.

She concentrates on amber, jet, pearls, opals, peridots, emeralds, sapphires, rubies and diamonds. There is no sense that she regards one as inferior to another: each is as good as its stories. Those she tells about amber range from a chunk found in a cave in Cheddar Gorge that is said to have been traded 12,500 years ago, to her own attempt to find out about mining at a gulag in Kaliningrad, to the Prussian Elector’s gift of the Amber Room to Peter the Great in 1716, which vanished during the second world war. Then we are in glamorous Whitby with jet, the fossilised remains of monkey puzzle trees that once grew densely over north-east Yorkshire. Never mind that jet went out of fashion with Queen Victoria, Finlay has some urgent news about the Romans, Cybele, a transvestite skeleton and a walk she took along the beach.

We are introduced to a retired pearl-fisherman on a housing estate in Scotland, who is ‘rarer than the pearls and … even harder to find’, before hopping to oyster farms in Japan and the story of Mikimoto’s cultured pearls. Opals take Finlay to Australia, peridots to Arizona; in Egypt, like one of those intrepid English lady travellers, she noses out Cleopatra’s emerald mines; in Sri Lanka she finds sapphires and in Burma rubies. Only with diamonds does she stay at her desk, apart from a modest dash to Antwerp.

This book plainly involved a huge amount of travelling, but it is only significant as it illuminates the scarcity and mystique of the gems. The point is always what Finlay finds when she gets there, both the stories and the stone itself. She is not satisfied until she has got to the source of the material and touched it, talked with miners and dealers, and placed them in a still unfolding history. Reducing the narrative of her own travels to the barest minimum helps to communicate the mesmeric effect of the jewels themselves. Their power transcends individuals not only because of their rarity but also because of the mysterious way in which they absorb stories, like inclusions. Anecdote and information accumulate with marvellous abundance and a passionate sense of the fascination of jewels, neatly held in place by a clear structure, like a clutch of trusty hairgrips. Buried Treasure itself feels like a wonderfully generous gift.

Finlay is helped, of course, by the fact that so many of the stories associated with jewels are dramatic ones. Tales of murder, love and corruption are two a penny, and this is particularly so with diamonds. It might then seem odd that the final chapter on diamonds should have less fizz than its predecessors. Finlay informs us that ‘of the estimated 3.6 billion diamond carats mined from 400 BC to date, some 40 per cent were discovered between 1991 and 2003’. Yet, even though they can be made artificially more successfully than other gems, their value has been sustained by clever marketing. But if Finlay herself sounds a bit exasperated by this, her account still remains engrossing. And it has one of the most extraordinary, hilarious conclusions I have ever read. Something really worth knowing about.

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