24 H. B. I'ATTON TOUHMALINE AND TOURMALINE SCHISTS 



schists. The bands vary in thickness, but are usually very thin, in some 

 cases not over one millimeter thick. 



This rock consists of quartz, tourmaline, and muscovite. Biotite, 

 although very abundant in the immediately adjacent mica-schist, is 

 usually entirely wanting in the tourmaline-schist. The tourmaline has 

 evidently been formed at the expense of the biotite. The grayish or 

 reddish portions are composed of quartz or of quartz and muscovite. 

 Feldspar appears to be entirely lacking. In many cases the main i)or- 

 tion of the rock is composed of a mass of quartz, with or without mus- 

 covite, through which run thin black lines of tourmaline. In still other 

 cases the quartz-muscovite mass is penetrated in two different directions 

 by parallel lines of tourmaline. These two series of black lines are some- 

 times almost at right angles to each other; at other times they make 

 sharply oblique angles. By their intersection with each other they thus 

 produce a beautiful reticulated structure. A still different structure is 

 produced when one set of these lines is sharp and straight while the 

 other is broad and wavy or crinkled. 



This tourmalinized schist is cut by numerous small sharp veins of 

 quartzor of quartz and muscovite. These vary fromalineto several inches 

 in thickness. They sometimes are parallel, but often cross each other. 

 These cutting veins not infrequentl}^ have affected the process of tour- 

 malinization, inasmuch as a more intense tourmalinization is to he 

 noticed in the immediate vicinity of the veins. Where much muscovite 

 is present in the veins this effect appears to be less marked. Coarser 

 crystals of tourmaline ma}' also be seen in these narrow veins, or they 

 may project slightly into the quartz mass of the vein. 



Under the microscope the tourmaline of this locality is seen to be very 

 similar to that of the first described locality. Usually the grains are 

 irregular in outline, or even very ragged, and then filled with quartz 

 inclusions. Frequentl}^, too, there occur small darker colored pleochroic 

 zones surrounding yellowish specks of either rutile or zircon or of some 

 similar mineral. Occasionally the tourmaline shows well defined pris- 

 matic habit with rhombohedral terminations. 



In addition to the above mentioned minerals, there also occurs a very 

 little muscovite in the sections studied. This scarcity of muscovite, 

 however, is only accidental, as it is ver}'' abundant in most of the hand 

 specimens. In addition may be mentioned a few small grains of a white 

 mineral with weak birefraction and strong index of refraction. They are 

 taken to be apatite. 



Photographic reproductions of these structures, as shown in figures 

 1 and 2, plate 1, and in figures 1 and 2, plate 2 (about one-half natural 

 size) give but a faint idea of the delicacy of the lines and of the beauty 

 of the original specimens, but they may serve to show the variety of the 



