70 The Apatite Deposits of Canada. 



es, unless some cheap means for separating the apatite can be 

 devised. It may be said, in general terms, that while some of 

 these true veins throughout portions cr the whole of theii breadth 

 yield good and pure apatite, others are of comparatively little 

 value. The bedded masses, on the contrary, are free from car- 

 bonate of lime, and although they may occasionally contain 

 small quantities of mica, pyroxene, hornblende, or pyrites, these 

 are seldom present to an injurious extent. 



The question of the continuity of these deposits of both 

 classes is an important one. Veins filling fissures that have been 

 formed in rocks are sometimes continuous for great lengths and 

 to great depths, but experience shows that their extent varies 

 very much for different regions and for different rocks. In- 

 clined beds, which were once horizontal sheets, inclosed in strata 

 that have since been folded, should be as persistent in depth a s 

 they are in length; and when traced in the outcrop for many 

 hundreds of feet, may be expected, under ordinary circumstances? 

 to continue downwards as far, unless a turn of the inclosing strata 

 bring them up again to the surface. The inclosed beds of 

 apatite in the regions already noticed are often traced for 500 to 

 1000 feet and more, and there is reason to believe that they are 

 continuous for long distances. The workings upon them have, 

 however, as yet been very superficial, generally from twenty to 

 forty feet, and rarely exceeding 100 feet. The deepest mine, 

 which is in Ottawa county, is now about 200 feet. 



The ordinary thickness of the bedded masses of apatite may 

 be said to vary from one to three and four feet, though not 

 unfrequently expanding to eight and ten feet, and even more, and 

 sometimes contracting to a few inches ; the same layer being 

 subject to considerable variations. In some cases the apatite in 

 a bed is found to thicken and then to diminish, or to be divided by 

 the interposition of the accompanying pyroxenic rock. The 

 condition of the apatite in these cases recalls the thickening and 

 thinning sometimes observed in a layer of coal among disturbed 

 strata, where, a* the result of great pressure attending the move- 

 ments of the harder inclosing rocks, it is alternately attenuated 

 and swollen in volume ; in which case a thinning in one portion is 

 necessarily compensated for by a thickening of the parts adjacent. 



The thickness of the veins also, as above stated, is very 



