THE ADIRONDACK GRAPHITE DEPOSITS 



65 



least before being folded, so that lateral differences in deposition 

 may well account for this. 



The Bear Pond schist. The northern arm of the Z-shaped 

 outcrop of the graphitic schist is a feldspar-quartz-biotite 

 graphitic schist. The feldspar dominates over the quartz while the 

 mica, usually phlogopite and biotite, altered in part to chlorite, 

 exceeds the amount of the graphite present. In the table showing 

 the results of quantitative microscopic analysis, the percentages by 

 weight of the constituent minerals are only approximate, but it is 

 believed that they are of the proper order of magnitude. The 

 minerals present in very small amounts and secondary alteration 

 (katamorphic) products are purposely omitted. To a very large 

 extent the feldspar is plagioclase almost entirely changed to second- 

 ary products, chiefly sericite. Likewise the phlogopite and biotite 

 are weathered partly^ to chlorite and serpentine. Not all the quartz 

 was an original constituent cf the arkosic sands of which the Bear 

 Pond schist is the metamorphic equivalent, for there has been an 

 introduction of silica. The graphite is entirely distinct from this 

 and its period of development must antedate this activity.. 



Fig. 13 Camera-luc'.da drawing of microscopic thin section 

 of Bear Pond schist from the "No. 2" pit, showing the 

 interleaving of the chloritic biotite and the graphite flakes 

 and the introduced pyritc. X 100. H. L. Ailing, 1918. 

 (Specimen No. 847). 



