'Every person on earth uses, either directly or indirectly, ten metric tons of minerals each year.' So write Dr R. V. Dietrich and Dr Brian J. Skinner in their new book Gems, Granites, and Gravels. Minerals and mineral products are involved in all aspects of our lives; we depend on them to keep us alive and ensure the continuity of our society. As a consequence, they have been a source of fascination and study throughout human history. In this book,...