XL] GEANITES AND GRANITIC VEIN-STONES. 195 



or of an admixture of this mineral with quartz, having the pe- 

 culiar structure of what is called graphic granite, or else pre- 

 senting a finely granitoid mixture of the two minerals, with 

 little or no mica, and with small crystals of deep red garnet. 

 Prisms of black tourmaline are also met with in these veins, 

 and more rarely beryl and even chrysoberyl. In the rock- 

 cutting on the Lewiston Eailroad, just below Topsham bridge 

 over the Androscoggin, there is a fine exhibition of these veins, 

 which present alternate coarser and finer grained layers, trav- 

 ersed by long spear-shaped crystals of dark mica passing from 

 one layer to another. 



1 7. A remarkable example of a vein of considerable dimen- 

 sions is seen in the feldspar-quarry in Topsham, which occurs 

 in a dark fine-grained friable micaceous schist. At the time 

 of my visit, in 1869, the limits of the vein were not seen, 

 though large quantities of white orthoclase and of vitreous 

 quartz had already been extracted. These were each nearly 

 pure, and in alternate bands, the quartz presenting drusy cavi- 

 ties lined with remarkable tabular crystals. One band was 

 made up in great part of large crystals of mica, and portions 

 of the vein consisted of a granular saccharoidal feldspar. The 

 famous locality of red, green, and blue tourmalines, with beryl, 

 lepidolite, amblygonite, cassiterite, etc., at Mount Mica in 

 Paris, Maine, is a huge granitic vein, which, with many others, 

 is included in a dark-colored very micaceous gneiss. 



18. In Westbrook numerous small veins of this kind, 

 holding coarsely lamellar orthoclase with black tourmaline and 

 red garnet, intersect strata of fine-grained whitish granitoid 

 gneiss. In Windham the dark-colored staurolite-bearing mica- 

 schist of this series is traversed by a granitic vein holding crys- 

 tals of beryl. In Lewiston a large vein of coarse graphic 

 granite, holding black tourmaline, and showing fine-grained 

 bands, cuts a great mass of bluish gneissoid limestone, which 

 forms an escarpment near the railroad, about half a mile below 

 the town. This limestone, which dips eastward about 15, is 

 interlaminated with thin quartzite beds, which are seen on 

 weathered surfaces to be much contorted. The bluish crystal- 



