B. J. Harrington — Formula of Bornite. 151 



Art. XY. — On the Formula of Bornite; bj B. J. 



HARHINaTON. 



The subject of the formula of bornite is one whicli has long 

 required investigation. If we refer to the standard works on 

 mineralogy we generally find that the formula of the crystal- 

 lized mineral is given as CugFeSg (or SCujS'Fe^Sg as originally 

 written by Plattner) and that numerous analyses of the massive 

 mineral from various parts of the world show little agreement 

 with this formula and often differ widely from one another. 

 The difference in the composition of the massive specimens 

 has been explained by saying that they were mixtures of bor- 

 nite with chalcopyrite and chalcocite, and no doubt in the case 

 of some analyses these or other mixtures have been called 

 upon to do duty for bornite. 



So far as the writer is aware, crystallized" bornite has not 

 been met with in Canada. The massive mineral of evident 

 purity, however, occurs at many localities, and it was thought 

 that an examination of carefully selected specimens might 

 throw some light on the question under consideration. Those 

 chosen were from widely separated points in the Provinces of 

 Quebec, Ontario, and British Columbia, and the results of 

 their analysis are as follows : 



I. II. HI. IV. V. 



Copper 63-55 62-78 62-73 63-34 63-18 



Iron 10-92 11-28 11-05 10-83 11-28 



Sulphur 25-63 25-39 25-79 25-54 24-88 



Insoluble _.. 0-30 0-38 0-24 



100-10 99-75 99-57 100*09 99*58 



Sp.gr. at 15°C 5-085 5-055 5-090 5-029* .... 



I. Harvey Hill, P. Q. 

 II. Bruce Mines, Ontario. 



III. Dean Channel, How Sound, B. C. 



IV. Copper Mountain, South Fork of Similkameen River, B. C. 

 V. Texada Island, B. C. The two last analyses were made 



by Mr. J. E. A. Egleson. 



It will be observed that the results agree well with one 

 another and also with the formula Cu^FeS^, which gives : 



Cu5FeS4 



Copper _ 63-27 



Iron 11-18 



Sulphur 25-55 



100-00 



* The fragment used for this determination contained a little malachite, 

 the eflEect of which would be to lower the specific gravity slightly. 



