AN:o24) The melting- and boilingpoints of metalloidsulphides. 11 



the surface. — Thus the theoretical reflections based on the 

 kiiowledge of the meltingpoints and the conditions of for- 

 mation in all known cases lead to the conclusion, that the 

 arsenicsulphides are deposited within the uppermost part 

 of the earths crust. It is in no way too much to suppose, that 

 also the veins and other deposits of unknown age in lime- 

 stones and shales were formed at a time, when the place of 

 occiirrence was not very far from the contemporaneous 

 surface. 



Stibnite occurs at many places with primary realgar and 

 auripigment, and is thus formed at temperatures considerably 

 lower than its own meltingpoint, The same may be said of 

 the numerous localities, where it is accompanied by cinnabar. 

 In other cases the stibnite itself is so to speak the geological 

 maximum thermometer. The most important of these depo- 

 sits are the, över the whole world spread, numerous gold- 

 carrying quarzveins with a little stibnite. Several mines in 

 Hungary, in Victoria, in Mexico and in the United States, 

 belong to this group of öres, and the geologists regard them 

 as formed at a slight or middling depth below the surface 

 of the earth. 



The guanajuatite is a very rare mineral and even the 

 tetradymite and the bismuthinite are considerably less com- 

 mon than the preceding minerals. The bismuthinite is in a 

 few localities found in larger quantities. — Of genetic interest 

 is the occurrence of bismuthinite near St. Etiénne, in the 

 Loire among the products of a burning coalseam. It is here 

 associated with the difficultly fused galena, and not with 

 volatile minerals like realgar and auripigment. A large 

 number of the bismuthinite and tetradymite localities are 

 contactdeposits and metasomatic öres formed at a consider- 

 able depth below the surface of the earth, which is testified 

 by the connection with abyssal rocks. Bismuthinite is often 

 found — although always in small quantities — in granite- 

 pegmatite' and to pegmatite related quarzveins, which can 

 not have been formed very near the surface. 



The molybdenite appears sporadically in a large number 

 of metasomatic and contact-ores, but its real home is in 



