no confusion between a red limestone and a red shaly limestone. A speckled 

 limestone is indicated by color stippling; mottled limestones, by mottled colors. 

 The dolomite symbol is a right-to-left diagonal dark-blue ruling. The back- 

 ground color is light blue, or the color of the rock. The same method is used 

 for evaporites, in which case the black-line symbol is drawn on the appropriately 

 colored background. 



Application of Color 



During the past 15 years the writer has experimented with a large number 

 of colored pencils, crayons, and various other mediums of color in their appli- 

 cation to geologic maps and well logs. In addition to the coloring phase, various 

 fixing or preserving materials have been tested. The following discussion is 

 based on this work. It is not held that other materials and methods are not 

 equally satisfactory, but that these methods are known to be reliable. There- 

 for, the use of specific trade names or brands does not necessarily signify a 

 quality superior to others; but, rather, that consistent results may be expected 

 when they are used. It is highly important to use only certain fixing mediums 

 with specific colored pencils; otherwise, the solvents in the lacquer may cause 

 the colors to run or mix, and in so doing ruin the log. 



There are two general types of colored pencils: the wax base or "water- 

 proof" and the indelible or water soluble. Use only the indelible type, regard- 

 less of the brand. The Mongol indelible colored pencil maintains a high degree 

 of uniformity in color hue and tone and in composition. It blends easily with 

 a charcoal blender and is not disturbed by lacquer. 



Colors on the logs are buffed to an even tone with blenders, or charcoal 

 stumps, which are composed of paper pulp. When colors are combined to 

 produce various intermediate hues, each application of the pencil is buffed before 

 the next is applied. The first color applied to the strip retains the strongest 

 hue in the mixture. For example, blue, then red results in bluish-purple; red, 

 then blue results in reddish-purple. 



The microscopist should experiment with mixtures of the different colors 

 so that he can readily match the colors of the rocks. When some knowledge 

 of the mixing of colors has been acquired, the work of plotting logs is greatly 

 diminished. The nine pencils listed earlier, together with drawing pencils of 

 two or three grades of hardness, are quite sufficient to make all the colors 

 needed for plotting a well strip. 



Plotting Templet 



The cellulose-acetate plotting templet is shown in Figure 3-1. When this 

 material is scratched deeply, or cut lightly, and then bent, it will break along 

 the scratch. The templet is made by carefully cutting lines along the outlines of 



44 



