PRECIOUS STONES.	1243
	the list of those gems for which figures were obtained directly from producers or persons closely associated with the production was very much smaller than usual. Furthermore, it is the aim of the Survey to give the value of all material in the rough, and the basis chosen for estimation is therefore, in many cases, not like that previously used, and hence, it has not been found possible for one not closely con­nected with the trade, as Doctor Kunz has been for many years, to give estimates of production on a. basis similar to that formerly used. Though Doctor Kunz has very kindly offered to supply the necessary information and has furnished assistance in many other ways, it has seemed best to rearrange the table of production to fit the informa­tion as furnished to this Office. In order that the changes made may be readily understood and a partial comparison be made with the pro­duction of precious stones in previous years, the table as printed in the report for 1905 by George F. Kunz is herewith reprinted in part. In the table for 1906 some large changes from 1905 have been re­corded in the production of certain precious stones. These have been caused in part by changes in the basis of estimation and in part by changes in production. The largest changes, where the same miner­als appear in both tables, have been in sapphire, turquoise, chryso-prase, tourmaline, and kunzite. In the case of sapphire, turquoise, and chrysoprase, the changes are due in part to the basis of esti­mation and in part to changes of production; in the case of tourma­line and kunzite, the changes probably result entirely from increased production. Production of precious stones in the United States in 1906.