USEFUL Jl//-.T.t/.> 



organic matter and found as a common inu,re.|ient of tli<-rm:il 

 springs. It has been detected by Daul>re and (iautier in sea 

 water. Native arsenic may result from the decomposition and 

 reduction of other ores of arsenic. \\ . II. Weed and L. V. 

 Pirsson report both realgar and orpiment from the hot -spring de- 

 posits of Yellowstone Park. G. F. Becker observed the sul- 

 phides of arsenic in a sinter at Steamboat Springs, Nevada. 

 They occur in seams in a sandy clay beneath the lava of Iron 

 County, Utah. Arsenic has been found in calcite in California, 

 and orpiment has been deposited in quartz crystals in Bosnia. 

 In Tyrol the sulphides of arsenic occur in association with 

 gypsum. Near Naples arsenic occurs as a product of volcanic 

 sublimation. Realgar and orpiment have both been found as 

 sublimation products of burning coal mines. 



The ready solubility of the sulphides of arsenic allows trans- 

 portation to a considerable distance from the original ore bodies 

 only to be reprecipitated through various agencies. Arseno- 

 pyrite is sparingly soluble in warm waters and from these solu- 

 tions it is known to recrystallize. Arsenolite, the white oxide 

 of arsenic, is an oxidation product of the native element or of 

 other ores of arsenic. Percolating arsenical solutions acting 

 upon the carbonates of other metals or upon calcite would give 

 rise to the arsenates of those metals or the arsenate of calcium. 



Character of the Ore Bodies. Native arsenic occurs in veins 

 in the crystalline rocks and the older schists. It is often asso- 

 ciated with ruby silver, antimony and the sulphide of zinc. 

 The sulphides occur in fissure veins with silver and lead minerals, 

 also in seams in sandy clays and as small crystals embedded in 

 clay. (See Fig. 97.) 



Arsenopyrite is by far the most important ore. It occurs 

 in well-defined fissure veins in beds, in threaded bands, and as 

 impregnation deposits in the country rock. 



Geographical Distribution. As already noted the arsenical 

 minerals are widely distributed in nature but the valuable com- 

 mercial occurrences are few. In the United States the areas 

 fall into three distinct belts: (1) The Appalachian belt; (2) 

 the Cordilleran district, and (3) the Pacific Coast belt. 



(1) The Appalachian belt stretches from Alabama on the 

 south in a northeasterly direction to Newfoundland. According 

 to H. Ries, one of the best known deposits of arsenopyrite occurs 

 at Rewald, Floyd County, Virginia. The ore deposit forms a 



