40 • Marine Minerals: Exploring Our New Ocean Frontier 





Box 2-A. — Mineral Resources and Reserves 



A general classification for describing the status of mineral occurrences was developed by the U.S. Geo- 

 logical Survey and the U.S. Bureau of Mines in 1976. The so-called "McKelvey Box" named after the then- 

 director of the USGS, Vincent McKelvey, further simplified the understanding of the economic relationships 

 of the mineral-resource classification system: 



r 



Cumulative 

 production 



ECONOIVIIC 



IVIARGIN- 



ALLY 



ECONOMIC 



SUB- 

 ECONOMIC 



IDENTIFIED RESOURCES 



Demonstrated 



Measured Indicated 



Reserves 

 Marginal reserves 



1 



Demonstrated 

 subeconomic resources 



Inferred 



Inferred reserves 



Inferred 

 marginal reserves 



Interred 



subeconomic 



resources 



UNDISCOVERED RESOURCES 



Hypotfietical 



Probability range 



^°i ' Speculative 



T 



The system is based on the judgmental determination of present or anticipated future value of the minerals 

 in place according to the opinions of experts. Below are the economic definitions on which the resource- 

 classification system is based: 



• Resource: Naturally occurring mineral of a form and amount that economic extraction of a commodity 

 is potentially feasible. 



• Identified Resource: Resources whose location and characteristics are known or reliably estimated. 



• Demonstrated Resource: Resources whose location and characteristics have been measured directly 

 with some certainty (measured) or estimated with less certainty (indicated). 



• Inferred Resource: Resources estimated from assumptions and evidence that minerals may occur be- 

 yond where resources have been measured or located. 



• Reserve Base: Part of an identified resource that meets the economic, chemical and physical require- 

 ments that would allow it to be mined, including that which is estimated from geological knowledge 

 (inferred reserve base). 



• Reserves: Part of the reserve base that could be economically extracted at the time of determination. 



• Marginal Reserves: Part of the reserve base that at the time of determination borders on being eco- 

 nomically producible. 



• Undiscovered Resources: Resources whose existence is only postulated. 



bearing beach sands were mined along the south- 

 ern coast of Oregon during World War II with gov- 

 ernment support. 



Gold has been mined from many beach placers 

 along the west coast of the United States and else- 

 where in the world. Marine placers of potentially 



minable gold are located in several nearshore 

 Alaskan areas in the Bering Sea, Gulf of Alaska, 

 and adjacent to southeastern Alaska. A commer- 

 cial gold dredge mining operation was begun by 

 Inspiration Resources near Nome in 1986, but a 

 number of nearshore gold operations in the Nome 

 area have been attempted and abandoned in the 



