Subsurface and Office Representation in Mining Geology 995 



on that portion of the note sheet; otherwise, there is no way of know- 

 ing which areas have been examined and which have not been examined. 



7. An efficient mapping system permits individuals or departments to 

 accompHsh their duties cooperatively with a minimum of confusion 

 and friction, and a maximum of efficiency. Professional draftsmen 

 post geologic data directly from note sheets prepared by the geologist 

 with little or no oral or written supplementary instruction. The ground 

 or excavation lines and other survey data are posted by the engineering 

 department or surveyor. Sampling done either by a sampling depart- 

 ment or the shift bosses is posted as assay data from sample sheets. It 

 is therefore imperative that every attempt be made to install a system 

 that is adaptable to cooperative map preparation. 



8. It is desirable that the number of maps be kept to a minimum with no 

 duplication, unnecessary scales, or overlap in area. The writer recalls 

 examining a mining property that had closed down for apparent lack 

 of ore. He was given a piano box crammed with maps of the mine. 

 No one had the slightest idea of the geologic and assay data available 

 in these miscellaneous odds and ends of maps compiled by various 

 operators during sixty years. When all the data had been replotted, 

 it was represented on fifteen sheets each 20" x 40". This integrated 

 information indicated a half-million-ton ore reserve of good grade al- 

 ready developed; and the operators were executing development away 

 from this ore on barren vein. 



9. Efficient working maps are prepared with the objective that revision 

 and correction can be readily made. 



10. Sectional representation is integrated with plan-map data. Because 

 there is no planning for efficient utilization of sections, much cross- 

 and longitudinal-section data are collected and lost in the files. At 

 some mining properties there are hundreds and thousands of subsur- 

 face sectional note sheets that are haphazardly oriented and filed. 



11. One condition of a good mapping system, often overlooked by mining 

 companies, large and small alike, is that notesheets and maps are filed 

 in a manner that geologists and draftsmen alike can readily and with 

 minimum eflfort locate notes or maps of any particular area or place. 



12. Coordinate values are carefully determined so that error and confusion 

 will be reduced to a minimum. Coordinate values are large enough so 

 that all points in the district are designated in terms of north and east, 

 never as west or south values. In other words any point within the 

 mineralized area is capable of location in positive or plus values and 

 never in terms of minus values; the zero value lies well outside and 

 to the south and west of the mineralized area regardless of property 

 boundaries. It is these zero areas that are the danger areas for "bon- 

 ers." In most cases 50,000 north and 50,000 east is about right for the 

 central portion of a district. 



13. Scales are such that detail is shown but not so large that areas covered 



