of some Chilian Minerals. Ill 



Lead ..... 5373 



Zinc 25'58 



Sulphur .... 20-69 



10000 

 so that the formula for this mineral would be 2PbS + 3Zn S. 



Taltalite. 



This new mineral has, since the year 1858, been found in 

 immense quantities in the mines of Senor Moreno, a short distance 

 inland from Taltal in the Desert of Atacama, constituting the 

 bulk of the supply of copper ores derived from those mines. It 

 is of a black or brownish-black colour, with from a dull up to a 

 satiny or vitreous lustre, and has a blackish-grey streak. It 

 occurs in masses consisting of an agglomeration of long crystal- 

 line fibres apparently quite pure, but sometimes accompanied by 

 Atacamite and copper-glance, which minerals are frequently 

 interposed between the fibres. An analysis by Domeyko afforded 



Protoxide of copper . . 44*5 



Lime 2-4 



Magnesia 0*8 



Alumina . . . . • 16*2 



Sesquioxide of iron . • 11*3 



Silica • 20-8 



Chlorine 0*7 



Water (? as ignition loss) 2*5 



9^2 



from which results he has not deduced any formula. 



The numerous specimens I obtained when in that part of 

 Chile are all so extremely homogeneous and crystalline in struc- 

 ture as to put aside the idea of this mineral being a mere mecha- 

 nical mixture, and enforce the conclusion that it is a definite 

 compound. 



The water which appears in the above analysis is most probably 

 not essential to its constitution, and in part at least is doubt- 

 lessly united with the chlorine and some of the copper present, 

 forming Atacamite, which, as before mentioned, is frequently 

 found inserted between the fibres of the minerals. Calculating 

 Atacamite as represented by the formula CuCl-f-3CuO-f 5BO, 

 the amount of chlorine present (0*7) would be equivalent to 4*56 

 per cent. Atacamite, which, if deducted from the above results 

 (along with the excess of water), and the quantities of the respec- 

 tive components recalculated to make up the hundred parts, will 

 give the following composition as that of the pure mineral : — 



