When we get to "The
Nesosilicate Subclass" we find, within it, about 20 pages on Imperial topaz and the history of its extraction at Ouro Preto; when we come to "The Cyclosilicate Subclass" we find 12 pages (3 short chapters) on emeralds, 30 pages (two chapters) on other colored beryls, and an extraordinary 100 pages on tourmalines, including individual chapters on, for example, the Cruzeiro mine, the Pederneira mine, the Santa Rosa mine, the Jonas mine, the Golconda district, northeastern Brazilian tourmaline-bearing pegmatites, and miscellaneous occurrences of uvite, dravite and schorl.