SCHISTS AND GNEISSES OF PORT HENRY LOCALITY. 255 



shreds, the former reaching: a centimeter across, and with it are many 

 green augites of niucli the same size and character. Pla<j:ioclase is seldom 

 lacking, and irregular bits of magnetite, shreds of biotite, titanite and 

 apatite appear in decreasing order of abundance. Red garnets, often of 

 large size, are very common, and masses of this mineral from an inch 

 to several inches across attract the observer's attention. Tbey have the 

 usual abundance of inclusions. In several localities, especially in Ticon- 

 deroga. scapolite has been found to take the place of feldspar, thus afford- 

 ing the same rock which has been observed by C. H. Smyth, Jr., on the 

 west side at the base of the limestone series. 



The graphitic Mica-schists. — At two widely separated points graphitic 

 mica-schist has also been noted. It is a thinly schistose, tender rock, 

 with a peculiar yellow, rusty outcrop, which belies its mineralogy, for 

 there is little of ferruginous minerals in it. It occurs abundantly on the 

 lake-shore just south of Cheever dock and in the interior of Moriah, 

 south of the Pilfershire mine. 



Under the microscope the rock is seen to consist chiefly of quartz of 

 all sizes, the largest being 1.5 millimeters in diameter. Plagioclase fol- 

 lows next, but is much less in amount and is frequently microperthitic. 

 Biotite and graphite also appear in irregular shreds. Some microsec- 

 tions show great richness in sillimanite, which forms mats and felts 

 and isolated needles. 



Dr F. D. Adams, with whom the writer visited the above localities, 

 states that these schists are common associates of the cr3^stalline lime- 

 stones in Canada. 



The Gneiss. — Assuming that the Cheever mine is in the limestone 

 series, as it appears to be, interesting data are available near the work- 

 ings. The ore, however, and its containing rocks are so similar to those 

 well within the areas of gneiss at Mineville that hesitation was at first 

 felt about this assumption, but the geologic section left no alternative. 

 Its walls afford massive gneisses. Next the ore, the hanging wall con- 

 tiiins j)lagioclase and an emerald-green pyroxene. A few feet further 

 the minerals are plagioclase, quartz, hornblende, and pyroxene, with 

 a notable microperthitic habit in the plagioclase. Fifty yards away 

 the rock contains microperthite, orthoclase, brown biotite, quartz, which 

 is often included in the feldspar, and almost no plagioclase. Similar 

 gneisses occur in other ])laces above the limestone, and mineralogically 

 they do not differ essentially from others below it. From this evidence 

 and that set forth in connection with figure G above, the impression hjvs 

 been strengthened that the limestones will prove to be merely a j)hase of 

 the great gneissic series A, to which reference has already been made in 

 tbc introduction. 



