Hate to disagree but Schumann is a poor choice. It is dated,
fraught wit h errors and the photographs are less than professional.
Surprisingly, the best overall book that combines, gemology, geology
and some connoisseurship is Max Bauer’s Precious Stones. The book
was origin ally published in 1909 so its dated and has no photos, but
it still is th e most comprehensive. Also its available in a two
volume Dover Edition f or about twenty bucks. For ID purposes GIA’s
Handbook of Gem Identificat ion is your best bet.
If your main interest is connoisseurship the field is a bit thin.
Zucker , B., A Precious Stones; A Connoisseur’s Guide, is excellent
even though the photos are uneven and its a bit dated. Another
Choice is; Federman, D., A Consumer’s Guide., in two volumes.
Federman is a bit glib but he i s up to date Great photos by Tino
Hammid. My own humble offering, The Ge m Aficionado; Secrets of The
Trade, should be out my Tucson 2003.