184 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1945 



requirements, and as depletion progresses the maximum or optimum 

 rate of production declines for reasons that need not be discussed here. 

 The availability of those minerals that are essentially byproducts, 

 such as antimony and silver, is further restricted by economic and 

 technologic factors that control the rate of production of the other 

 minerals with which they are associated. Nine of the 33 minerals 

 shown on the chart are available in quantities equivalent to more than 

 a 100-year supply at the prewar rate of use. Only four fall within 

 the 25-to-100-year supply bracket, while eight qualify in the 5-to-25- 

 year group. The reserves of the remaining 12 are small, representing 



COMMERCIAL RESERVES COMPARED WITH 1935-39 ANNUAL RATE OF USE 



I Years supply remaining 1944 



1CAKS 



o to 



Bosed on proved reserves only 

 NOTE- Figures indicate quantitative significance of estimated reserves only They do not imply that the reserve could sustain consumption 

 ai the assumed rote for the full period shown. 



Figure 5. — Commercial reserves of certain minerals as of 1944 expressed in 

 terms of years life at average annual rate of consumption 1935-39. 



less than a 5-year supply. The significant point is that if we make 

 a division at the 35-year level, a period but little more than the usual 

 interval between wars, 21 of the 33 minerals fall below the line, and 

 this group includes petroleum, copper, lead, and zinc in the production 

 of which we have led the world for many years. 



The rate of production the remaining reserves can support in the 

 future is no less important than the size of the reserve. Production 

 of those minerals of which we have over a 100-year reserve could be 

 expanded to meet any demand that can reasonably be expected. Mod- 

 erate expansion of postwar production of sulfur, fluorspar, and natural 

 gas over prewar peak rates doubtless could be accomplished if justified 

 by economic conditions. It is doubtful if copper production could be 



