988 Subsurface Geologic Methods 



for widths as well as assay value, the product of the width and value may 

 be plotted instead of value alone. 



Valuation of Mining Properties 



A geologic examination of a mining property might have two aims: 

 one, the finding of ore, and the other, the placing of a value on the prop- 

 erty. The first is based on geologic knowledge and deductions corrob- 

 orated by exploration. The second aim, that of valuation, is based in part 

 on geologic knowledge but also on numerous economic conditions. It is 

 not the purpose of this chapter to discuss valuation or appraisal; recent 

 books cover in an adequate manner the many ramifications that must be 

 considered before a value may be placed on a mining property.^"* ^^ ^^ ®^ 

 The mining geologist may be called upon to prepare the final valuation 

 report, or he may work with the mining engineer, furnishing him geologic 

 information. The basis for all valuation is the grade and amount of 

 known ore and the possible future production. The measured, proved, or 

 positive ores are easily accounted for in the valuation, but rarely is much 

 ore blocked out in a property that is being examined for possible pur- 

 chase. In most cases the mine either is relatively undeveloped or for 

 some economic reason appears to be worked out. For properties of this 

 sort, geology is of prime importance in estimating future production from 

 possible, prospective, or inferred ore reserves. The future of many mines 

 depends upon the accuracy of predictions or deductions made by the 

 mining geologist. 



Questions 



1. Classify ore deposits. 



2. Discuss the procedures commonly used in exploration and develop- 

 ment work. 



3. Discuss structural control stressing its importance as an aid to ore 

 search. 



4. Distinguish between: 



a. Geochemical and biogeochemical guides 



b. Hypogene and supergene solutions 



c. Stratigraphic and structural control 



d. Opaque and non-opaque microscopic examination 



e. Scales used for underground and surface geologic mapping. 



5. Discuss the importance of wall-rock alteration. 



6. Outline a geologists duties in an exploration and development pro- 

 gram. 



7. Define sampling, and outline sampling methods and precautions. 



8. Discuss the illustrations necessary to represent information obtained 

 from an exploration and development program. 



8*McKinstry, H. E., op. cit., pp. 459-502, 1918. 

 ^ Forrester, J. D., op. cit., pp. 491-573, 1946. 

 "<' Jackson, C. F., and Hedges, J. H., op. cit., pp. 58-76, 1939. 



*' Parks, R. D., and Whitehead, W. L., Examination and Valuation of Mineral Property, 3d ed., 

 Cambridge, Mass., Addison-Wesley Press, Inc., 1949. 



