CONCBETIONS ^^^I^P 105 



Concretions which appear at first sight of possible organic origin occur 

 in the western part of the Moose Eiver district (Woodman, 1904, page- 

 24) . It is unnecessary to redescribe them here, but it may be said that 

 careful examination of slides failed to show the slightest organic trace. 



The slates of the Halifax formation are highly altered by contact meta- 

 morphism west of the city of that name, on the shore of the harbor. As 

 they were originally more varied in texture than most of the rocks of this 

 group, the changes have emphasized the coarse and fine layers strongly. 

 Near York redoubt, Halifax harbor, arenaceous strata abound in concre- 

 tions up to the size of a hen egg, and isolated, although occurring persist- 

 ently along the same beds. Finer sandy layers have smaller concretions 

 closer together, often coalescing. The topography of these forms is 

 varied, but in no case do they give evidence of organic origin or contents. 



The best concretions yet found in the series by the author come from 

 Gays Eiver mines, locally also called Coldstream. They lie besidp i hvonk 

 in the horizon which marks at this place the contact of the Goldenville 

 formation with the Lower Carboniferous gold-bearing conglomerate, the 

 plane of their major diameters occupying the stratification planes. In ap- 

 pearance they are extremely regular, thickened, circular discs, averaging 

 .3 to .5 by .2 inch. Each is clearly distinct from the inclosing slate, 

 differing in this and other respects from concretions elsewhere in the 

 series. The lamination of the rock bends around them, so that they 

 stand out as eyes in the slate. Cleavage has not affected them, while ren- 

 dering the adjacent layers thoroughly fissile. They are so well cemented 

 as. to withstand a strong percussion or compression. In color they are 

 like tlie slate, but less greenish, and often stained copper brown from 

 iron carbonate in the overlying conglomerate. 



In the slide they appear with, a comparatively clear center of quartz 

 grains, coarser than in any other part of the mass. Surrounding this is 

 a region of mixed quartz, calcite, kaolin, and a small amount of a grayish 

 substance as yet undetermined. Outside of this is a ring, broadly ellip- 

 tical in section, apparently of kaolin closely cemented by iron oxide. The 

 greater ease of fracturing of the clear central part in comparison with this 

 margin is noticeable. Adhering to the main concretion here and there 

 are strips of the chloritic slate in which it was formed. Although appar- 

 ently, when examined in the field, especially favorable as a possible rest- 

 ing place of fossils, these concretions have not been shown to contain any 

 organic nucleus. 



One mile south of Lower Argyle, on the west coast of the province, a 

 ledge of slightly schistose quartzite beside the post-road has on its weath- 

 ered surface pits which are of either concretionary or organic origin. 



