ECONOMIC GEOLOGY. 20,1 



Whilst augite is so common the mineral orthoclase on the other 

 hand is very seldom met with. Where it is plentiful, as in some 

 rocks of R£s Koh, it is associated with augite, forming an augite- 

 syenite. The diorites and granophyric diorites usually contain 

 nothing but plagioclase felspar however great may be the proportion 

 of quartz. Olivine is very plentiful even in rocks that are not basic, 

 as was already noticed by General McMahon. 1 Sphene and apatite 

 are often very abundant. 



It is to be hoped that an opportunity may arise for completing 

 the study of such an interesting collection. Many questions that 

 require further field investigation cannot be elucidated for some- 

 time to come on account of the inaccessible situation of some of the 

 most typical cutcrops. But enough material has been gathered to 

 repay a thorough study of the collection. 



Section 2.— Economic Geology. 



Ores of copper, lead, and iron, and some other minerals of com- 

 mercial value, such as sulphur, sulphate of lime and sulphate of alu- 

 mina, have been met with in several localities. Some of them occur 

 in small pockets as an original constituent of some of the igneous 

 rocks mentioned in previous chapters. All the others are results of 

 solfataric action, either in the recent volcanoes, or in connection 

 with some basaltic intrusions that belong to an earlier period. None 

 of the deposits observed are of great richness, and the physical 

 drawbacks of the region, the absence of fuel and the difficulty of 

 obtaining labour make it improbable that any satisfactory returns 

 could be obtained under existing conditions. 



Some of the varieties of travertine formerly deposited by hot 

 springs connected with volcanic activity might be used as an 

 ornamental stone. 



Silicate of copper, or "chrysocolla ,, occurs disseminated through 



Silicate of copper s yenite in the Ris K6h, south of Charsar in the 



occurring as a constituent gt t f Kharan, and through diorite, in the 



mineral of some igneous > & » 



rocks - Lar Koh in Persia, near Malik-i-Sidh-K6h, 



1 Quart. Journ. Geol. Soc, Vol. Ill (1897), p. 29?. 

 I ( 113 ) 



