THE PALMER GNEISSES. 215 



windin«' in and ont among the other com])ouents, and aiding in emphasizing 

 the schistosity. In most of the sections examined the parts of tlie crnshed 

 quartzes have been separated, and into the crevices between them the matrix 

 has been forced, thus producing a genuine fragmental structure. 



The matrix in which the quartzes he is a uniform felt of kaolin, mus- 

 covite, a few flakes of chloi'ite, a little biotite, small masses of calcite, tiny 

 grains of quartz, and remnants of feldspar. The sericite and kaoHn are the most 

 abundant components. Their leaflets are usually arranged approximately 

 parallel to the planes of fohation in the rock, except where they occur in the 

 crevices between fractured quartz and feldspar grains, when they are per- 

 pendicular to tlie walls of the crack. They bend around the larger quartzes, 

 enveloping them in concentric layers, and wind in and out between neigh- 

 boring grains like the matrix of many squeezed porphyries. Occasionally 

 the remnants of feldspar left between the meshes of the matrix are optically 

 continuous over large areas with the outlines of granitic feldspar grains, but 

 usually when they can be detected they give evidence that they too, like the 

 quartzes, were fractured and their })arts separated during the production of 

 foliation in the rock. 



By far the greater number of the Palmer gneisses are as simple in 

 composition as those above described. A few present special features that 

 should be mentioned. A number of specimens collected from various 

 points all along the belt are dotted on their surfaces with plates of a dark- 

 green chloritoid,^ varying in size from '2 mm. to almost microscopic dimen- 

 sions. A rock (specimen No. 21999) from about 1500 steps N., 750 steps W., 

 of the SE. corner of sec. 32, T. 47 N., R. 26 W. (Atlas Sheet XXXII), is a 

 good type of these. Its bowlders constitute a large proportion of those 

 occurring in the conglomerates southwest of the Piatt mine. In the hand 

 specimen the rock i-esembles a decomjjosed gneiss. In its thhi section quartz 

 gi-ains are rare. Only an occasional one, or a quartz mosaic with the outlines 

 of a gi-ain, is found here and there through the schistose matrix, which is a 

 uniform mass of sericite and kaolin flakes, with a little fine-grained quartz 

 mosaic. Embedded in the matrix, in positions irrespective of the schistosity, 

 are large plates of the green chloritic mineral, nimierous grains and irregular 



' Cf. A. C. Lane, Rept. State Board of Geol. Surv. for 1891-92, p. 182, Lansing, 1893; and W. H. 

 Hobbs, Am. Jour. Sci., 3d series, Vol. L, 1895, p. 125. 



