SULPHURET OF LEAD. 49 



of the vein, the ore is imbedded in a gangue of carbonate of lime, with druses of calcareous 

 spar of great beauty, and presenting a great variety of crystalline forms. The average width 

 of this gangue is about four feet. As usual, the proportion of the gangue is quite variable, 

 the ore being in some parts nearly pure, and easily separable from the walls ; while in others, 

 nearly the whole of the vein is made up of calcareous spar. 



The common metallic associates of galena are also found here, viz. iron and copper pyrites 

 and zinc blende, although the latter is of rare occurrence. 



Two specimens of galena from this mine were subjected to analysis, with the following 

 results, viz : 



I. II. 



Sulphur, 13.20 13.26 



Lead, 85.40 85.35 



Carbonate of lime, and loss, 1.40 1.39 



No. I. was part of a cubical fragment detached from the gangue. It had a specific gravity 

 of 7.500. 



No. II. was of a hghter colour, and somewhat silvery appearance. This peculiarity is 

 probably caused by a tarnish, or perhaps by the contact of the gangue. 



This ore also contains a minute proportion of silver, which may be separated by the process 

 of cupellation, but which can hardly be detected by the humid process. 



The lead ashes, as it is commonly called, found in great abundance on that part of the 

 Rossie vein which was exposed to the atmosphere, and which invested most of the surface 

 specimens of galena, proved to be a mixture of the carbonate and sulphate of lead and car- 

 bonate of lime in variable proportions. The formation of this compound was undoubtedly 

 due to the reaction of the carbonate of lime and sulphuret of lead, together with a free ex- 

 posure to atmospheric influence. 



For three or four years, this mine was worked with great activity, and shafts were sunk to 

 the depth of upwards of one hundred and fifty feet. At this depth the vein presented similar 

 appearances to those observed nearer the surface, except perhaps that the proportion of ore 

 to the gangue was somewhat less. Fine druses of crystallized galena and calcareous spar, 

 together with variously modified crystals of iron pyrites and some copper pyrites, were from 

 time to time laid open. A few beautiful specimens of crystallized sulphate of strontian, of 

 a bluish colour, were also found. 



Since 1839, however, this mine has not been worked, whether in consequence of the in- 

 sufficient supply of ore, the expense of raising it, or the large previous outlay, it is unneces- 

 sary now to inquire. 



A short distance from the preceding, towards the road leading from Rossie to Oxbow in 

 Jefferson county, is the Jepson vein, which has a bearing south 88° 30' east. It has pro- 

 duced a large quantity of ore, and was thought to be little inferior in vakic to the Rossie vein. 

 Its gangue and associated minerals arc also similar. 



Part I. 7 



