172 



Subsurface Geologic Methods 



need further study. Papers by Ingerson and Ramisch,^^ Anderson,^^ and 

 Ingerson and Tuttle ^^ point to the origin of quartz grain shapes. 



MICRO (PETROGRAPHIC) ANALYSIS 

 WARREN R. WAGNER and JOHN W. GABLEMAN 



Microscopic analysis of rocks is such a well-established field of study 

 that this paper is not intended to be an exhaustive presentation of the 

 methods developed to the present time. The writers wish only to call to 



Figure 71. Schematic drawing of the fold in figure 64, showing in simplified form 

 the types of statistical diagrams to be expected from mica flakes in a tight fold. 



the attention of students and workers some of the applications of the micro- 

 scope to rock examinations. 



Many micro-techniques are time-consuming and expensive; therefore, 

 the first duty of the investigator is to decide upon the method that will 

 produce the desired information with the minimum cost. 



In general, two types of microscopes are availiable: (1) the petro- 



" Ingerson, Earl, and Ramisch, J. L., Origin of Shapes of Quartz Sand Grains: Am. Mineralogist, vol. 

 27, pp. 595-606, 1942. 



^ Anderson, J. L., Deformation Pliines and Crystallographic Directions in Quartz: Geol. Soc America 

 Bull., vol. 56, pp. 409-430, 1945. 



^* Ingerson, Earl, and Tuttle, 0. F., Relations of Lamellae and Crystallography of Quartz and Fabric 

 Direction in. Some Deformed Rocks: Am. Ceophya. Union Trans., vol. 26, pt. 1, pp. 95-105, 1915. 



