OF CENTRAL CANADA PART II. 



77 



FIG. 43. 



A garlic-like 



22. Arsenical Pyrites or Mispickel: Colour between silver-white 

 and pale steel-grey, often obscured by yellowish or pale-blue tarnish; 

 streak, greyish-black. Crystallization, Rhombic : the crystals mostly 

 small and short rhombic prisms, terminated by two 

 nearly flat and striated planes (Fig. 43). Occurs 

 also in granular and irregular masses. H = 5.0 

 6.0; sp. gr. 6.0. 6.4. BB emits a strong odour 

 of garlic, and melts into a dark magnetic globule, 

 odour is also more or less perceptible when the mineral is broken by 

 a smart blow. One hundred parts contain : Sulphur 19.6, Arsenic 

 46.0, Iron, 34.4 ; but a small portion of the iron is occasionally re- 

 placed by cobalt.* 



This mineral is useless as an ore of iron, but it serves for the pro- 

 duction of arsenious acid, the " arsenic " or " white arsenic " of 

 commerce, and it frequently contains minute portions of gold. In 

 Central Canada, it occurs in the Laurentian strata of Marmora and 

 Tudor. Specimens from Marmora have yielded the author amounts 

 of gold ranging from 1 oz. to over 6 ounces in the ton of 2000 

 Ibs.t In Tudor, small crystals of mispickel J accompany Bismuth 

 Glance. The copper-ore veins of the Huronian rocks, also show here 

 and there small crystals and granular masses of this mineral, as at 

 the Bruce and Wellington Mines ; and it occurs in small quantities 

 in some of the argentiferous veins of the Upper Copper-bearing 

 Series around Thunder Bay, Lake Superior. The altered rocks of 

 the Eastern Townships, south of the St. Lawrence, likewise contain 

 it in places, as near the Chaudiere Rapids in the County of Beauce, 



* In this case, the roasted ore when fused with borax will import a more or less decided blue 

 colour to the glass. For details respecting this and other blowpipe processes and reactions see 

 Part 1. 



t An amount of this kind, it will of course be understood, although rendering the ore of great 

 commercial value, does not practically affect the normal composition of the mineral. One 

 ounce per ton of 2000 Ibs., for example, is equivalent only to a percentage of 0.00343. 



J Although a reference to minute crystallographic details 

 is opposed to the plan of the present work, it may be 

 stated, here, that these Tudor crystals present the com- 

 bination shown in the annexed Figure, in which the 

 common brachydome Jjg is replaced by $% and & . The 

 form ^ , the summit angle of which equals 118 30', is a 

 comparatively tare form, but it appears to be always 

 present in the cobaltiferous varieties of Mispickel, and in 

 the allied species Glaucodot. The Tudor crystals, as 

 shewn by a blowpipe examination, contain a small per- 

 centage of cobalt. 





FIG. 44. 



