39 I4 ZJ 7l 1531 1t 22 22 L2 L7 L7 43 T2 Source: U.S. Bureau of Mines. Connoali tv Data.Sumng-r.i9s, -1972f 1923J 1974t Ig7s,' L- L:r9:r97'L9:r97\9-E; Donalal A. Brobst and vralalen P. Pratt, eds., "united states !'lineral E;6;;;;;, c,eological s\l r vey Professionar PaPer 820 (washingbon D'c' t u' s' Governnent Printlng office, I9?3) t U.s. Bureau of Mines, !'finer al9-{Parbook 1948 and 1974 (washlngton D.c.: U.s. Government Printing offlce, 1950, 1975) The entire table is based uPon The Future of Non-i\rel Mlnerals (washington' D.C. I The Brookings Institution, L977). pP' 6-7' A/37 /386 Engl ish Annex Page 36