INTERESTING LOCALITIES OF MICHIGAMME FORMATION. 459 



parallel arrangement. In this vai-iety of the rock it is evident that the 

 mineral particles have been flattened or moved differentially, or both, and 

 thus were adjusted to one another. In many of the slides a great deal of 

 feldspar is found mingled with the quartzose background. In those which 

 show an intermediate degree of alteration a portion of this feldspar is clearly 

 clastic. In the rocks which are nearly completely crystalline, what part is 

 clastic and what part a secondary development is very difficult to determine. 

 In the most coarsely crystalline mica-gneisses found, orthoclase, microcline, 

 and plagioclase are all seen. The individuals for the most part average 

 about the same size as those of the quartz. Certain of the larger feldspar 

 areas have a fragmental appearance, but the finer-grained background has 

 clearly recrystallized. 



In the more metamorphosed varieties of the schists garnet and staurolite 

 are abundant. The garnets often have very well developed crystal outlines. 

 As they grow they seem to be able to absorb or push aside nearly all of 

 the other constituents, as they are comparatively free from inclusions, 

 although oftentimes a considerable amount of quartz and feldspar is 

 contained The staurolite occurs in the ordinary twinned forms. Very 

 often their outlines are ragged; at other times they have sharp crystal 

 boundaries. As the staurolites have developed, they have grown arovmd the 

 quartz and feldspar, so that these minerals within the staurolite crystals are 

 nearly as abundant as in the remainder of the section. However, in the 

 growth the staurolite has absorbed or pushed aside the muscovite, biotite, 

 and chlorite, as these are rarely included in it. The staurolite shows 

 no evidence of strain. Occasionally large blades of chloritoid are seen. 

 These, like the staurolite, include the quartz and feldspar, but exclude the 

 mica. These blades are in general arranged with their longer diameters 

 and cleavage transverse or at a large angle to the foliation of the rock. It 

 is believed that the lack of dynamic effects in the staurolite and the trans- 

 verse arrangement of the chloritoid are CNadence tliat these minerals and 

 the garnet developed under static conditions, after movements ceased. If 

 this be true, it is probable that the micas and chlorite had largely developed 

 at an earlier time, and if so the chloritoid, garnet, and staurolite must have 

 grown by absorbing the micas and chlorite. 



