Kemp — Geology of Essex County. 611 





Haber- 



SMAW. 



Rossi. 



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Lkdoux. 





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Fe 8 4 



87.20 



82 . 37 



73.62 







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none 



0.017 



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none 



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0.08 







Fe 



63 . 45 



59.56 



53.62 



55.62 



54.80 



After engaging a guide and a boat, 1 rowed down the river and coasted 

 the east shore of lake Sanford to a point somewhat east or south of east from 

 Big island. We then walked about three-fourths of a mile up hill to the east, 

 to an opening on the Sanford ore-bed, very near the location of the crossed 

 hammers on the map. Considerable ore had been blasted and taken away a 

 short time before. The location was about 300 feet above the lake. A breast 

 about thirty feet wide by fifteen feet high was exposed with no wall rock 

 appearing. It apparently trended northeast, as I followed float ore with no 

 outcrops for a hundred yards. All the loose surface rock met was anor- 

 thosite. The ore both in the lump and in the breast "contains occasional 

 crystals of green plagioclase, in instances three or four inches in diameter. 

 They show the characteristic situations, but are so thickly charged with 

 minute green augites that a millimeter from the edge, as shown by thin 

 section, they are practically opaque. Each is surrounded by a reaction rim, two 

 to three millimeters wide, of biotite and brown hornblende, so that in no case 

 does the feldspar actually touch the ore. They are extremely curious and 

 interesting phenomena. Undoubtedly the feldspars are original crystalliza- 

 tions from the igneous magma precisely like the ore itself, and becoming 

 involved in it, these rims of minerals of intermediate composition were 

 produced by the reaction of the two on each other. Some samples of ore 

 have given curiously high percentages of alumina, and, as earlier remarked, 

 these included feldspars are in part responsible for it. 



