THE STONE OF HEAVEN: Unearthing the Secret History of Imperial Green Jade Adrian Levy, . . Little, Brown, $24.95 (432pp) ISBN 978-0-316-52596-1 ...

This astonishing Imperial Chinese spinach green jade seal of the Qianlong period (1736-1795) is set to fetch more than £1million when it goes under the hammer at Bonhams in London.

Thanks partially to Chinese demand, rare imperial green jade, a translucent stone that's been compared to fine emerald, is the most expensive gem in the world, worth more per gram than diamonds.

A Qing Dynasty imperial white-jade seal was sold for a record HK$95.9 million ($12.4 million) in Hong Kong, double what it fetched in 2007 as Chinese buyers vied for the rarest antiques ...