British Mineralogy, 351 



black; fracture subconchoidal, uneven, and granular; brittle; 

 powder black; hardness 3*5, scratching calcite but not nuor. 

 Specific gravity taken on 61*96 grains pure fragments was 4*97 

 at 60° F. 



Before the blowpipe, on charcoal, it decrepitates, and then 

 fuses to a globule which, when treated "'in the oxidizing -flame, 

 covers the charcoal with a white sublimate of oxide of anti- 

 mony; and still nearer to the globule sublimates of the oxides 

 of zinc and of lead may be perceived, whilst sulphurous acid is 

 evolved ; with borax or charcoal the glass reacts for iron, whilst 

 antimony ; and sulphur are given off and by continued treatment 

 in the oxidizing-flame a white metallic globule containing silver 

 and copper is obtained, which, when treated with phosphate, 

 shows the copper-reaction. 



In the open tube sulphurous acid was evolved, and a white 

 antimonial sublimate formed. 



When a weighed quantity was fused with borax and lead, 

 treated with the oxidizing-flame, and the resulting silver-lead 

 cupelled, as in the ordinary blowpipe assay, the mineral yielded 

 13"9 per cent, of silver. 



A preliminary qualitative examination having shown the mi- 

 neral to contain sulphur, antimony, iron, silver, copper, zinc, 

 lead, and a little insoluble quartz, the quantitative chemical ana- 

 lysis was conducted as follows. 



A quantity of the finely pulverized mineral was introduced 

 into a previously tared small glass-tube boat open at both ends, 

 and weighed ; it was then introduced (close up to the bend) into 

 a hard-glass tube, the one end of which was cut off obliquely 

 and bent, so as to dip into a two-necked bottle containing a so- 

 lution of tartaric and hydrochloric acids, whilst the other neck 

 was provided with a bulb-tube inserted into the liquid only 

 so far that the solution could only be forced up into the bulb, 

 but must fall back again. A current of dry chlorine gas w r as 

 now passed through ; the arrangement and the part of the tube 

 containing the mineral was then heated gradually until it ap- 

 peared perfectly decomposed and converted into chlorides. The 

 tube-boat was now drawn back with a wire out of the hard-glass 

 tube in which it had been heated, and allowed to absorb mois- 

 ture slowdy by being kept for some hours in a glass beaker mois- 

 tened on the sides with water. The hard-glass tube was now 

 washed out with hot water into the solution of hydrochloric and 

 tartaric acid contained in the two-necked bottle. 



This operation consequently resulted in the formation of two 

 products, respectively : — 



A, a solid residue contained in the tube-boat, which contained 

 all the silver in the form of chloride, the insoluble quartz, a 



