500 mckelvey. SEDIMENTARY MINERAL DEPOSITS [Ch. 27 



but also of underground workings, pit faces, and other openings. Usu- 

 ally a number of geologic maps at various scales are prepared and 

 kept up to date as the work progresses. Even if systematic geologic 

 mapping is not done, generally the location of at least the workings 

 and mine installations are shown on some kind of map. 



In some mines where much drilling or sampling is required in the 

 eourse of development or mining, much of the geologist's time may be 

 consumed in describing samples and logging core. The drudgery in- 

 volved often is compensated, both to the geologist and to the com- 

 pany, by the results obtained in the interpretation of the data so ac- 

 cumulated, for no better means exists for learning the habit of the 

 deposit than to combine mapping, sampling, and daily observation of 

 the faces. 



Another function of the mine geologist may be the periodic estima- 

 tion of reserves. The reserves so estimated generally include only 

 material blocked out and ready for mining ("measured" reserves in 

 the strictest sense). Such estimates involve much less interpretation 

 than do those prepared in the appraisal of the property as a whole, 

 for the position, thickness, quality, and structure of the deposit in the 

 block in question are well known, the cutoff grade has been established, 

 and, in short, the approximate limits of the rock to be mined have 

 already been ascertained. 



PROCESSING 



Many sedimentary mineral products are in a form suitable for mar- 

 keting as they come out of the ground. Others require only simple 

 treatment, such as grinding, drying, or sizing, and still others require 

 beneficiation or purification by complicated chemical or mechanical 

 methods. The principles utilized in this phase of mineral production 

 are those of metallurgy and mineral dressing, a field that is well ad- 

 vanced. The geologist, and especially one trained in the methods 

 of sedimentary petrography, may make significant contributions to 

 processing, however, through his knowledge of the texture, composition, 

 mineralogy, and mass properties of the rock, or his familiarity with 

 methods for determining them. 



THE FUTURE OF THE FIELD 



A candid account of the extent to which geology is actually used, 

 rather than the way it could or should be used, in the production of 

 sedimentary materials emphasizes two observations made previously: 



