5S4 



Report of the State Geologist. 



and a basic garnetiferous, gneissoid rock (No. 40) were in the same ledge and 

 not over one foot apart. No. 41 is a gneissoid variety again. On nay return 

 from this trip into the mountains my horse ran away and spilled these 

 specimens all along the highway, so that I lost them and cannot give the 

 mineralogy more accurately for this reason. At Nos. 55 and 56, gneissoid 

 anorthosites again appeal- that show in thin section the familial 1 crushed 

 feldspar, and in this case a little hornblende and diallage. Away down in 

 the southeast, gneissoid norites appear, that contain labradorite, hypersthene, 

 emerald-green augite, hornblende and garnets. A little quartz also appears, 

 and a tendency in the plagioclase to develop a mieroperthitic texture that 

 resembles the rocks regarded as members of the typical gneisses. Inter- 

 mediate varieties of this character are extremely difficult to satisfactorily 

 place in stratigraphic relations, and lead one to concede great possibilities to 

 metamorphism. The aspect of the rock, however, is clearly igneous and its 

 relations are with Series III. Another extended stretch of gneissoid rocks is 

 in the ridge on the east bank of the Branch above tipper Jay, and extending 

 into Keene. Under the microscope, No. 35 exhibits brown hornblende, a 

 little green pyroxene, more or less crushed labradorite and deep pink garnets. 

 It is considered also to belong to Series III. 



Two exposures of dark basic gabbros have been met in or near the town. 

 One, No. 4, in the northeast, was not over twenty-live feet thick, in quartzosc 

 gneisses on each side. It is a typical gabbro like the one near the Cheevcr 

 mine, at Port Henry. The second exposure is in the town or near its line in 

 Lewis township, on the southeast. In the thick woods above Sprncemill 

 creek, appears a large exposure of dark green olivine gabbro, No. 59. The 

 familiar reaction veins between the feldspar and the ferro-magnesian silicates 

 are present. 



Series IV. The Palaeozoic sediments fail entirely in this town. The 

 Potsdam sandstone to-day is not found much farther up the Ausable river 

 than Keeseville, unless it is buried under the sands and gravels, but it is not 

 improbable that it has had a more extended outcrop in earlier time. 



Series V. No diabase or other related dikes, except the gabbro described 

 mil lei' Series III above, were met. 



Series VI. The great deposits of sand and gravel that were mentioned 

 in my previous report, page 464, and that are especially well developed along 

 the Ausable river, cover a goodly portion of the northern part of Jay. 

 Especially on the flanks of Clark mountain and in the neighboring parts of 

 Wilmington they spread out as stretches of sand, covered by a second growth 



