RAW QUARTZ, ITS DEFECTS AND INSPECTION 351 



For inspecting twinning and direction of optic axis, the stones were viewed 

 horizontally through the polarizing filter E and window, with mirror /'' 

 removed (using mercury lamp .1). Normally the operator looks directly 

 down into the mirror to see the same view. For observing other interior 

 defects, the view is from directly above the tank, through the fluid surface 

 (with projection lamp in housing // being used). This is the normal manner 

 of observation. B mounts heat and color filters;C is a polarizing filter with 

 diffusing surface; E, a polarizing filter crossed to polarizer C; 6', a glass win- 

 dow; and // is a rudimentary lamp house normally fitting over A to edge 

 of B. The tank D has two rectangular windows parallel to C and E, and a 

 circular window in rear wall for entrance of projection illumination. 



Fig. 4.5 — The inspectoscope and stones used for the following figures. See also Fig. 4.3 



Most of the following photographs are of stones shown, Fig. 4.5, on the 

 drain pan and in the tank. Note that stones 3, 6, 9, 12, 14 are well faced 

 stones; 9, 7, 13 have fractured surfaces; and 15 is typical river quartz (nearly 

 perfect internally). The special manner of orienting the stones in the tank 

 to obtain the desired views will appear from the following descriptions. The 

 views are one-half to full size. 



Figure 4.6 is a polarized light view of a wedge shaj)ed l)asal section (one- 

 fourth inch thick at the left, to three-fourths inch thick at the right). The 

 wedge is viewed along the optic axis with the plane faces approximately 

 perpendicular to the line of sight (i.e., parallel to the polarizer C of Fig. 4.5). 



