8 Mr. D. Forbes' s Researches on the 



system. The prisms are found striated parallel to their longer 

 axis, and twins are most common. Lustre metallic; colour 

 tin-white to steel-grey, tarnishing quickly to a greenish-grey 

 tinge. The crystals, when situated in quartz, are frequently 

 coloured a fine green on their surfaces, evidently from the 

 nickel present. The ore also, when exposed to the air and 

 weather, assumes a fine apple-green colour from the same cause. 

 Streak black to dark grey. Fracture uneven, brittle. Specific 

 gravity 4*7 at 60° Fahr. A chemical examination was made by 

 Mr. Philip Kroeber which gave the following results : — 



Arsenic . 



43683 



Sulphur . . . 



16755 



Iron .... 



34-932 



Nickel . . . 



4-741 



Cobalt . . . 



trace 



Silver .... 



0-090 



Gold . . . 



0-002 



Antimony . . 



trace 



100-203 



Mispichel. — Another variety of mispickel, occurring likewise 

 in veins in the lower Silurian formation, is found at Inquisivi in 

 Bolivia, where it is associated with Danaite, native bismuth, and 

 an undetermined and probably new mineral in hexagonal crystals 

 with perfect basal cleavage and having a great resemblance to 

 dark brown zincblende, in a large quartz vein. 



The crystals obtained were too imperfect for measurement, 

 but evidently belonged to the trimetric system ; no defined 

 cleavage-plane was observed. Colour dark steel-grey ; lustre 

 dull metallic ; streak dark greyish black. Non-magnetic. Hard- 

 ness 5*5, scratching apatite, but not orthoclase. 



The specific gravity at 60° Fahr. was found to be 6*170. 



Before the blowpipe in a closed tube it gave off, first some 

 trace of sulphur, then sulphide of arsenic, and lastly metallic 

 arsenic. 



In the oxidizing flame it gave off sulphur and arsenic ; and 

 with borax glass, slagged off entirely with reaction for iron, but 

 showed no appreciable quantity of copper, nickel, or cobalt 

 present. 



An assay by cupellation afforded a trace of silver containing 

 gold, which latter appeared present in larger quantity than 

 the silver. 



The analysis was performed exactly as in the case of the mis- 

 pickel from San Baldomero mine, with the exception that the 

 arsenic was determined as loss. The results were as follows : — 



