THE BARITE DEPOSITS OF MISSOURI 59 



noted. The limonite (locally called "iron") causes trouble in 

 mining when it adheres to the barite. If much of the barite 

 shows limonite, the diggings are abandoned. Some very large 

 masses of limonite were seen in the Richwoods district. The 

 color of the yellow soil is due to this mineral. 



Hematite. — Hematite is not very common in the barite de- 

 posits proper, except that the red color of the clay in which they 

 are found is due to it. Occasionally masses of limonite with a 

 coat of hematite were found. This is a clear case of dehydration. 

 The brilliant red color of the Potosi and Proctor residual clays 

 is due to this mineral. They contain 12.04 per cent of ferric 

 oxide, largely in the form of hematite. 



Carbonates 



The following carbonates were found: calcite, dolomite, 

 malachite, smithsonite, and cerussite. 



Calcite. — Calcite was never observed in the residual deposits. 

 It is found in some solution or vein deposits. The most notable 

 occurrence is one on Indian Creek where there are honey-color- 

 ed crystals of calcite weighing 50 pounds or more. Some of the 

 crystals are well-developed, scalenohedrons, although limited 

 space has often prevented facial development. In this occur- 

 rence part of the calcite was earlier than the barite and part was 

 later. At the Eye mine some small crystals of calcite were found 

 which were rounded scalenohedrons. When the veins are ex- 

 posed to weathering at the surface the calcite soon disappears. 

 Considerable calcite is found in some of the mines in the Central 

 district. 



Dolomite. — Dolomite was not observed in the veins or the 

 residual deposits, except in so far as it was a constituent of the 

 surrounding rock. It lines a great many cavities in the dolomite 

 some of which have been filled with barite. That this has been 

 the case is shown by the fact that one surface of the barite has 

 casts of the dolomite crystals. The barite under the clay is usually 

 more or less mixed with a dolomite sand (the "sand rock" of the 

 miners) which is the result of the disaggregation of the dolomite 

 under the influence of weathering agencies. 



Malachite. — Malachite is found in small slender crystals, 

 radiating clusters, and as a green powder. It appears at several 



