32 UNIVERSITY OF MISSOURI STUDIES 



dolomite crystals are of a beautiful rose color, and are about an 

 eighth of an inch in diameter. The ciystals of the dolomite are 

 largely anhedral with irregular outlines, but an occasional rhom- 

 boidal face appears. Large crystalline masses of calcite are 

 found thruout the formation. The grains of both these minerals 

 show dust-like particles under the microscope. Other constitu- 

 ents are barite, glauconite (rare), pyrite (rare and altered to 

 limonite near the surface), and scattered masses of chert. 



The chert is in places rarely more than 5 to 6 inches in di- 

 ameter and most of it is in pieces less than an inch across. The 

 shape of these masses is very varied. The chert is very dense 

 and usually is white or light gray in color. It is not possible to 

 say that chert is especially abundant in any one part, and, on the 

 whole, it is a minor constituent of the formation. 



The barite appears in veins, as irregular masses, and as dis- 

 seminated grains. Its occurrence will be discussed fully later. 



The composition of the Proctor formation is shown by the 

 following chemical analysis : 



SiOs 86% 



^'^ I 15 



AI2O3 Trace 



CaO 30.38 



MgO 21.36 



CO2 46.62 



H2O 32 



99.69% 

 The formation is thick-bedded, the beds being from 2 feet 

 to 10 or 12 feet thick. In this area the beds are essentially hor- 

 izontal. Near the base in one or two localities the weathered 

 layers have a suggestion of being thin-bedded, but, on the whole, 

 the beds are massive. On Clear Creek some of the beds show cross- 

 bedding on a minor scale. Near the base there are abundant 

 stylolites, some two inches long. They are parallel to the bedding 

 planes in so far as their position was determined. They are es- 

 pecially well developed at the old diggings about two and one- 

 half miles northwest of Potosi, and along Rocky Branch, a tribu- 



