British Miner a logy . 181 



Inverary mineral was examined; and although several other 

 specimens of the purest mineral obtainable were assayed for 

 nickel,, none of them yielded a higher percentage of that mineral 

 than the above. 



Gersdorffite. 



Locality : Craigmuir nickel mine on the side of Loch Fyne, 

 eight miles below Inverary, Argyllshire, where it was found by the 

 author in April 1855, occurring in a small string or crosscourse 

 intersecting the main lode of sulphide of iron and nickel. This 

 mineral does not appear to have been previously observed as a 

 British species, and is not noticed in Greg and Lettsom's l Mine- 

 ralogy of Great Britain. y It is not improbable, however, that 

 the smaltine which, in page 302 of that work, is stated to occur 

 in " Argyleshire, at Essochossan Glen, two miles from Inverary, 

 dispersed in small bright patches in Eisennickelkies/'' may in 

 reality prove to be this mineral. 



The specimen here described was broken out, in the deepest 

 part of the mine, from a small string of nearly pure Gersdorffite, 

 about from 1 to 2 inches wide. It was a compact aggregate of 

 minute indistinct crystals along with quartz and a talcose mine- 

 ral. In places patches and strings of copper pyrites were visible ; 

 but little or no sulphide of iron and nickel occurred with it, not- 

 withstanding that this last-mentioned mineral formed the mass 

 of the main lode, and the object of the explorations. The Gers- 

 dorffite had not as yet attracted the attention of the miners. 



By pulverizing the ore and washing in a batea, it was found 

 quite easy to obtain the Gersdorffite in a nearly pure state, in the 

 shape of irregular crystalline grains and fragmentary crystals, 

 which, however, were not sufficiently perfect to enable its crystal- 

 line form to be settled with certainty, although it appeared to be 

 monometric. 



The characters of this mineral are as follows: — crystallized; 

 opake; lustre metallic ; colour white to greyish white, tarnishing 

 to a greyish-brown tinge; streak black; powder blackish grey; 

 fracture granular; brittle; hardness 3*75, rather below fluor- 

 spar : the specific gravity, taken on two different specimens of 

 the crystalline grains previously washed as free as possible from 

 adherent quartz, was found to be respectively 5*65 and 5*49 at 

 60° F. 



Heated in a closed tube the mineral decrepitates and gives off 

 a considerable sublimate of reddish-yellow sulphide of arsenic, 

 which is transparent both whilst hot and cold. In an open tube 

 it yields a similar sublimate, along with a white one of arsenious 

 acid, and evolves sulphurous acid. Heated with soda on char- 

 coal, the residue reacts strongly for sulphur when placed upon 



