8 NEW YORK STATE MUSEUM 



The quartz grains are fairly clean and free from the innumerable 

 dusty inclusions which characterize some sandstones and quartzites, 

 containing only rutile needles sparingly distributed, a few liquid 

 and gas inclusions, and an occasional minute zircon. The feldspar 

 grains are perfectly fresh and are made up almost wholly of micro- 

 cline, microperthite, crv-ptoperthite, and an unstriated feldspar 

 resembling oithoclase. 



Quartz and feldspar make up practically over 98 per cent of the 

 rock; tourmaline is next in order of abundance, with sericite and 

 biotite in minute crystals closely following. Special interest is 

 attached to the tourmaline because of the relatively large amount 

 of it in a rock of this type, and because of its rather perfect form; 

 the tourmaline in this rock does not represent former original worn, 

 rounded, clastic grains. It occurs in interpenetrating relations, 

 in fairly well-defined prismatic forms, and in ragged patches, the 

 mode of occurrence suggesting replacement effects and actual intro- 

 duction of material during or subsequent to the reorganization of 

 the rock. 



Titanium-bearing minerals are unusually abundant; rutile, in 

 shapeless grains, in aggregates of grains, and in minute, well-defined 

 crystals ; ilmenite, both fresh, and partly, and sometimes wholly 

 leucoxenized ; and what was judged to be titanite, are widely 

 disseminated. The presence of these minerals accounts for the 

 0.39 per cent Ti02 found during the course of the chemical analysis 

 (table i). In addition to the occasional minute zircon crystals 

 included in the quartz grains, there are also larger and more or less 

 rounded zircons sparingly distributed throughout the rock. 



These features are illustrated in figures i to 4 inclusive ; figure i 

 shows the distribution of minerals other than quartz, and figure 2 

 shows the same field taken with nicols crossed. This serves to 

 emphasize strongly the individual grains and to illustrate their 

 structural habit, already described. Figure 3 shows the variability 

 in grain size common to these rocks, and a zircon crystal of unusual 

 size. Figure 4 shows the strongly schistose phase of the Poughquag 

 in this area ; this material is of too poor quality to be of use. 



The chemical analysis of the rock is given in table i ; the silica 

 is too low (95.51 per cent) and the alumina too high (2.35 per cent) 

 for its use in the manufacture of glass, ferro-silicon, or silica refrac- 

 tories. In addition to the constituents determined, the rock carries 

 manganese, zirconia, alkalies, magnesia etc. in very small amounts. 

 The structure of the rock is good, affording possibility of its use 



