Mineralogy of South America. 137 



or brown colour, translucent, and probably a felspatbic mineral. 

 It was impossible to get the sand quite free from this admixture ; 

 but taken as pure as possible to obtain, the specific gravity of 

 the black mineral was found to be 4*34 at 60° F. (15°'5 C). 



The sand was not entirely decomposed by hydrochloric acid 

 even when previously heated in a current of hydrogen, during 

 which operation it lost in weight, and afterwards dissolved in part 

 in hydrochloric acid, with the evolution of hydrogen gas. 



The chemical examination w T as therefore made by fusing a 

 known quantity in the state of fine powder along with ten times 

 its weight of bisulphate of potash. The fused mass when quite 

 cold was dissolved in cold distilled water, which left behind a 

 small amount of white insoluble silica amounting to 3*32 per 

 cent. The filtrate, much diluted with water, was acidified by a 

 little nitric acid, with the intention of retaining all iron in solution, 

 when, after prolonged boiling, it deposited a considerable amount 

 of faint yellow-coloured titanic acid, which, however, became 

 brown upon ignition, evidently from still retaining some sesqui- 

 oxide of iron. This titanic acid amounted to 57*72 per cent, of 

 the mineral's original w r eight. Approximatively, therefore, the 

 mineral may be regarded as being composed of — 



Titanic acid (with some Fe 2 O 3 ) . 57*72 



Oxides of iron 38*96 



Insoluble silica 3*3.2 



100-00 



From which it w r ould appear that the mineral belongs to the 

 variety of titanoferrite called by Von Kobell " Kibdelophan." 

 The analysis of the original kibdelophan from Gastein afforded 

 that chemist* — - 



Titanic acid . 59*00 



Protoxide of iron 36*00 



Sesquioxide of iron .... 4*25 

 Protoxide of manganese . . 1*65 



lOOIX) 

 whilst its specific gravity was found to be 4*661. 



Epsomite. — This mineral is said to occur in very large quantity 

 in the mountains near Hilo, south of Ariquipa in Peru, and is sent 

 into the interior of Peru and Bolivia, w'here it is employed medi- 

 cinallyf' It is stated to occur in veins; but in what formation is 

 at present unknown, though it may be presumed to be a product of 

 the volcanic action which is common to the whole of that district. 



* Scliweigger-Seidel's Jour n. fur Chemie und Physik, vol. Ixiv. p. 245. 

 f I liave to thank M. Falkenheimer of La Paz for extremely large and 

 fine specimens of this mineral. 



