Harrington — Interesting Variety of Fetid Galcite. 345 



Art. XXX YI. — On an Interesting Variety of Fetid Galcite 

 and the Cause of its Odor ; by B. J. Harrington. 



About fifty years ago, when Sir W. E. Logan was studying 

 the geology of the Grenville region in Canada, he came upon an 

 interesting variety of calcite in the township of Chatham (lot 

 10, range xi) which emitted "when rubbed an overpowering 

 odor like that of sulphuretted hydrogen."* In the " Geology of 

 Canada," published in 1863, Dr. T. S terry Hunt again called 

 attention to what is evidently the same material, as follows : 

 "We may here notice a peculiar variety of fetid carbonate of 

 lime, which forms a large bed in the Laurentian series, in Gren- 

 ville. It is a very coarse-grained, cleavable, milk-white and 

 apparently pure calcite, which when struck or very lightly 

 scratched, evolves a most powerful and unpleasant odor, recall- 

 ing somewhat that of phosphuretted hydrogen. It dissolves 

 without residue in dilute acids, and the carbonic acid gas 

 evolved does not affect solutions of lead or silver salts, so that 

 it is difficult to say to what the peculiar smell of this singular 

 rock can be due. It is entirely distinct from the bituminous 

 odor, which is evolved by percussion from a great many of the 

 limestones of the Palaeozoic series, or from that produced by 

 striking some siliceous rocks." 



Specimens of this interesting calcite have long been in pos- 

 session of the writer, and it was felt that it should be possible 

 to arrive at some definite conclusion with regard to the cause 

 of the fetid smell. Thin sections were in the first instance 

 studied and showed under the microscope the presence of great 

 numbers of very minute cavities, evidently containing a liquid, 

 as moving bubbles due to the contraction of the liquid could 

 occasionally be seen. These cavities suggested the presence of 

 hydrogen sulphide in a liquid condition or possibly in solution 

 in water. If the gas were present in either condition, it was 

 obvious that it would be liberated either by solution of the 

 calcite in an acid or by pulverizing the mineral ; further, 

 that the finer the degree of pulverization the more hydro- 

 gen sulphide would escape. This was fully confirmed by 

 experiments made both by the writer and by Mr. Lloyd 

 Lodge, demonstrator in the chemical department. It has been 

 found, moreover, that Hunt's observation with regard to the 

 action of the escaping gas upon solutions of lead or silver salts 

 is erroneous, for in both cases black precipitates are obtained, 

 while in the case of cadmium salts the characteristic yellow 

 precipitate is produced. The inference would appear to be 



* Geological Survey of Canada, Report of Progress, 1853-54-55-56, p. 23. 



