Finlay explores the histories of the traditional precious gems plus amber, jet, pearl, opal, and peridot. She usually centers each chapter around a certain mine or processing locale: for sapphires, a gem market in Sri Lanka, where jewels are traded among certain locals like so many Yu-Gi-Oh cards; for jet, Whitby, England, source of Queen Victoria's mourning jewelry and goth Mecca due to its role in Dracula; an Arizona mountain on an Apache reservation that's the world's largest supply of peridot (though it's not commercially mined due to conflicts in the tribal government).
Her travels are fascinating, though there's a lot that's dispiriting at the same time. For example, much amber these days is melted and molded, sometimes with bugs stuck in to create an aura of millions-of-years-old authenticity. De Beers' early mines were staffed with convicts effectively "bought" from the South African government who were denied even clothing when they went to bed at night (lest they hide jewels, of course). Burmese ruby miners today aren't kept in much better conditions. Hardly anyone who actually mines stones (no matter what the stone may be or where the mine) gets rich; the buyers always seem to have a chokehold on the market through stockpiling. And cultured pearls are formed by cutting open an oyster's genitals and forming a wound that takes months to heal. (Yeah, it's an oyster, but I dunno, man.) But there's a good deal that's intriguing and beautiful, as well, such as a hunt for Cleopatra's abandoned emerald mines or a collection of jars holding a new type of man-made opals sitting on a shelf in an Australian miner's garage. I'm far more behind lab-created gems after reading this book, though.
There are a couple flaws in Jewels; it is still a bit long, and there're a couple points that could've used expansion: Finlay talks, for example, about how peridot was once highly valued but now is out of favor, but she doesn't really tell the story of why and how, despite promising to do so. I can, though, overall happily recommend this volume; it's reassuring to see an author set back on the right path.
(But I can't get jet. You're wearing coal, people. Come on.)