44 NEW YORK STATE MUSEUM 



largely of rather homogeneous, serpentinous material (bluish gray- 

 interference tints) which is apparently igneous glass into which ser- 

 pentine marble has been fused. Occasional well-formed laths of 

 plagioclase and many specks of magnetite occur. The outer i or 

 2 millimeters of this zone are very rich in magnetite specks. This 

 zone shows a rapid transition into the next one. 



Zone 4 One-third of an inch wide. Reddish brown, glassy look- 

 ing. Apparently good igneous glass filled with many tiny specks of 

 what seem to be magnetite and perhaps lo per cent of plagioclase 

 mostly in laths but some in stout prisms with distinct zonal struc- 

 ture. This grades perfectly into the next zone. 



Zone 5 One-half of an inch wide. Pale green color and much 

 like no. 4 except for absence of the tiny specks. The green color 

 is due to serpentinous material which appears to have been absorbed 

 by the molten mass. The contact between this and the next zone is 

 rugged though pretty sharp. 



Zone 6 Ordinary bluish black diabase from within the dike and 

 with no serpentinous admixture. This rock is mostly a dark glass 

 which contains 5 per cent plagioclase laths and 5 per cent pale red- 

 dish brown, euhedral augite crystals and numerous specks of pre- 

 sumably magnetite. 



PALEOZOIC OUTLIERS 



No actual outcrop of Paleozoic strata has been found within the 

 borders of the quadrangle, but certain nearby Paleozoic outliers 

 have an important bearing upon the geologic history of the region. 

 Two of these outliers have been described by Professor Kemp, one 

 of them being Little Falls dolomite which occurs at Schroon Lake 

 village (Schroon Lake sheet), and the other being Potsdam sand- 

 stone which occurs near the village of North River (Thirteenth 

 Lake sheet). 



During the summer of 19 10 the writer discovered a small Paleo- 

 zoic outlier i mile south of the map edge and i mile due west of 

 High Street village (Luzerne sheet). The exposures are rather poor 

 and small but the rock is quite certainly in place with the strata 

 lying in nearly horizontal position. Both sandstone and dolomite 

 beds occur and it is not certain whether the rocks represent the pas- 

 sage beds of the Theresa formation or the contact between the Pots- 

 dam and the Little Falls dolomite, though the former is more prob- 

 able. This outlier lies at 1400 feet elevation and not far to the west 

 of the No. 9 mountain fault and on its downthrow side. 



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