TOURMALINE IMPREGNATIONS AT CONTACT 25 



structures involved. All the dark colored lines in these reproductions 

 represent tourmaline, while the light colored portions are mostly quartz. 

 In figure 1, plate 1, and in figure 2, plate 2 may be seen the cross-hatched 

 structure produced by narrow streaks of tourmaline crossing each other. 



Third Locality : Tourmaline impregnating Schist at Contact with 

 SMALL Pegmatite Veins 



Some 1,500 feet farther along the road beyond the first locality, just 

 where one first comes in sight of the " Rocky Mountain ranch," occurs 

 a vein of pegmatite about two to three feet in width. This vein runs 

 straight up and down the hill at right angles to the road. It divides into 

 branches which enclose " horses " of schist. The cleavage of the schist 

 and the vein strike in the same direction. Here, too, the schist, which 

 is very micaceous, is impregnated with tourmaline on both sides of the 

 pegmatite vein, as are also the enclosed horses. The streaks of tourma- 

 line run parallel to the vein and to the rock cleavage. The vein may be 

 traced about 200 feet down the hill. Farther down are other veins of 

 pegmatite, striking in the same direction and accompanied by similar 

 alteration of the schist at contact. 



At this locality the country rock has not been extremely altered at 

 contact with the pegmatite veins, and the rock cleavage has not been 

 apparently lessened. The schist here is a friable, soft mica-schist of a 

 beautiful bronze-like luster. Near the contact it contains minute, deli- 

 cate prisms and needles of black tourmaline scattered thickly but very 

 irregularly throughout the mass. In places this tourmalinized rock has 

 a well defined crinkled structure. 



Under the microscope the tourmaline is seen to be in sharply defined 

 prisms which often show double termination, one end having a very flat 

 rhombohedron and the other end a less flat rhombohedron. Light yel- 

 low to blood red stains of iron oxide abound and explain the bronze-like 

 luster of the rock. Quartz is not very abundant and the biotite is present 

 only in traces. 



Discussion as to Origin of these Tourmaline Rocks 



As to the origin of these tourmaline rocks it is evident that at the last 

 two localities they are local modifications of the mica-schists which form 

 the country rock, and are limited to a narrow zone of contact Avith veins 

 of pegmatite. In all three localities, and this applies to all occurrences 

 of tourmaline seen by the author in this region, the tourmaline occurs 

 only in or near veins. This mineral does not appear to form an impor- 

 tant constituent of the surrounding schists. In a few cases, however, the 



