THE ADIRONDACK GRAPHITE DEPOSITS 85 



of garnets and the particular slide examined failed to show any 

 sillimanite. Whenever the Laurentian granite is found its habit 

 invariably is to saturate, to soak into, and inject a quartzose forma- 

 tion and leave the more calcareous and ferruginous beds unaffected. 

 The Hague gneiss, except for the minerals that furnish the custom- 

 ary earmarks, is essentially a feldspathic quartzite. Garnet and 

 sillimanite are regarded by most petrographers as indicating or 

 strongly suggesting metamorphic action. The writer would there- 

 fore maintain that these two minerals are not reliable or consistent 

 characteristics of this formation but may be due to the Laurentian 

 granite which is absent at the Rowland property. This Hague 

 quartzite is decidedly purer than its equivalent at Hague. 



At the Hooper property we saw that a para-amphibolite strati- 

 graphically lies beneath the Hague gneiss. This was tentatively 

 named the Dresden. Its presence on the Rowland property at this 

 horizon fits in with the general scheme of things. This amphibolite 

 is about 65 feet thick, which is exposed on the western slopes on the 

 knob to the northwest of the mine. Below the para-amphibolite is 

 a limestone formation which we have not before encountered. This 

 I propose to call the Johnsburg limestone, of which only the top 

 portion was seen, so the total thickness is unknown. 



The Algoman granite is exposed at the village of Johnsburg, but 

 lies at no great depth under the sedimentary rocks, up through 

 which it has sent numerous pegmatites and profoundly affected the 

 Dixon schist. 



Structure. The knowledge of the succession of the beds was 

 applied to the problem of the structure. The mill is situated in a 

 low depression between two low hills, the one to the north being 

 of some prominence. The latter is composed almost entirely of the 

 Hague quartzite dipping south. Although the summit of the hill 

 is higher than the mine, it represents a horizon stratigraphically 

 beneath the ore ; hence the Dixon schist has been eroded and no 

 ore to the north of the shaft in the immediate vicinity can be 

 expected. This hill is an anticline, while the low dome to the south 

 of the hill is a syncline in a north and south section which in reality 

 is a structural basin, with its major diameter probably lying in an 

 east and west direction. The actual extent to the east is not 

 definitely known. The accompanying reconnaissance map perhaps 

 brings out this idea better than a description. The semicircular 

 swing of the graphitic schist is entirely inferred from the occurrence 

 and behavior of the Swede Pond and the Hague quartzites, as well 



