178 Mr. D. Forbes' s Researches in 



Sulphur . . 



. 34-21 



Iron |. . . 



. 44-60 



Nickel. . * 



. 5-24 



Copper . . 



. 1-32 



Rock-matter . 



. 14-63 



100-00 



The rock-matter (14*63 per cent, in all) contained a consider- 

 able amount of quartz, along with no less than 5*2 per cent, mag- 

 nesia in combination, but only a trace of lime. 



Iron Pyrites. — In the sulphide of iron and nickel obtained 

 from this mine it is very usual to perceive that the bronze colour 

 of the mineral is blotched or studded over with brass-yellow spots 

 more or less round, and varying in diameter from one-sixteenth 

 up to even occasionally half an inch across ; the colour and hard- 

 ness of these parts confirmed the supposition that these spots 

 were iron pyrites. It was, however, only when, after the lapse of 

 some years, the pyrrhotine had become quite broken up and dis- 

 aggregated, that it was easy to obtain these portions of the spe- 

 cimens for analysis. 



When the pyrrhotine fell to powder by the action of the atmo- 

 sphere these particles were quite unaffected, and were seen to be 

 so many irregular spheres of cupriferous iron pyrites which ex- 

 ternally retained still a sort of skin or crust of pyrrhotine, but, on 

 breaking, at once showed that the mass possessed the bright 

 brass-yellow colour characteristic of pyrites. 



Upon making a determination of the specific gravity, it agreed 

 with that of pyrites ; for, several of these globules being taken, 

 pulverized, and the magnetic external crust of pyrrhotine removed 

 by a magnet, the mineral was found to possess the specific gra- 

 vity 4-93 at 60° E. 



The analysis was conducted in a similar manner to that of the 

 last mineral, excepting only that the copper was precipitated by 

 sulphuretted hydrogen ; and the nickel and cobalt present were 

 separated from one another by treating the mixed oxides obtained 

 in the course of the analysis by Plattner's process before the 

 blowpipe. 



15-55 grs. yielded O'Ol gr. insoluble quartz, 0*03 gr. free sul- 

 phur, 7*64 grs. sulphate of barytes, 0°64 gr. oxides of nickel 

 and cobalt, 0*23 gr. oxide of copper, and 10-16 grs. sesquioxide 

 of iron . Reducing these data to percentages, we have the com- 

 position as follows : — 



