356 GEOLOGY OF THE SECOND DISTRICT. 



(p. 354). Tlie whole vein in the face of the ledge was thus laid bare, the galena appearing 

 in the central part of the calcareous spar, in a white or silvery stripe, being coated with disin- 

 tcgi'ated carbonate of lime, mixed, it is said, with a small quantity of carbonate of lead. The 

 sulphurel of this vein is coarse crystalline as a whole, but mixed occasionally with the fine 

 grained and more silvery looking ore ; but the latter is always, or has been thus far, only in a 

 small proportion to the coarse-grained galena. 



A fact of some consequence to be known is the low level of the region in the neighborhood 

 of the mines, and indeed of the whole town of Rossie. It is scarcely over one hundred and 

 fifty or two hundred feet above that of the River St. LawTence ; and yet a stranger passing 

 through this section of country would very likely call it mountainous. The hills are frequent 

 and steep, and the valleys at their bases are upon the level of the St. Lawrence. Hence, in 

 mining, where the mines are even situated upon the highest of the hills, the shafts are soon 

 sunk to the level of standing water. 



Leaving out of view all economical considerations in regard to the Coal Hill mine, there 

 are several points which are interesting both to the geologist and mineralogist. 



Soon after the vein was opened, a large geode, or cavity termed a water course by miners, 

 was struck. This course was found lined with crystals of galena, whose edges bounding the 

 faces were three inches in length. Some of the single crystals weighed thirty-five pounds ; 

 generally thej' came out in groups, whose aggregate weight exceeded one hundred pounds ; 

 and it was not uncommon for five or six crystals to be aggregated together, in which case 

 four or five faces of each crystal were well exposed. Some of these large crystals presented 

 smooth polished faces, but generally they were rough and uneven ; and frequently they were 

 coated with carbonate of lime, which was readily detached, leaving a smooth polished sur- 

 face. The crystals, however, instead of being perfect cubes, were more or less modified by 

 the replacement of the solid angles. One of the common modifications was the passage of 

 the cube into the regular octahedron, Ijy the replacement of the solid angles ; more rarely, 

 the edges were replaced ; and in a few instances, both modifications appeared together. The 

 large crystals were usually confined to the water-course first opened ; all parts of the vein, 

 however, furnished smaller cavities, which were invariably lined with crystals of galena and 

 calcareous spar. Among the latter we found small crystals with fine polished surfaces, per- 

 fectly finished in all respects, and possessing the brilliancy and lustre of polished steel. The 

 smaller crystals have the same modification as the larger. Associated with galena in the 

 geodes, are crystals of sulphuret of iron, which for brilliancy and finish exceed any which 

 have been found in this country. The ordinary form is the cube, witli the modification lead- 

 ing to the pentagonal dodecahedron. The replacements upon the edges in this case vary from 

 a slight removal of an edge to a deep truncation, ending with the perfect form of the dodeca- 

 hedron. A less common and more complicated modification, is the combination of the octa- 

 hedron and rhombic dodecahedron with the cube. Such are some of the common or predo- 

 minant forms, both of lead and pyrites, at the Coal Hill mine : the details in relation to 

 them belong to my colleague, Prof. L. C. Beck, the Mineralogist of the Survey. 



