RECORDS 101 



SECTION OF GEOLOGY AND MINERALOGY. 



February i8, igoi. 



Section met at 8:15 P. M., Dr. A. A. Julien presiding. 

 The minutes of the last meeting of Section were read and ap- 

 proved. 



The following program was then offered : 



George I. Finlay, The Granite of Barre, Vermont. 



A. A. Julien, Note on a Sand Fulgurite from Poland. 



Summary of Papers. 



Mr. Finlay described the occurrence of the Barre granite as 

 a single intrusion through the country rock, which is a biotite- 

 schist, in the southern portion of Barre township. Many inclu- 

 sions of the schist are found in the granite, and this rock has 

 almost surrounded other masses of the schist, which remain in 

 place, with their original dip and strike unchanged. The 

 speaker employed a series of original lantern views to illustrate 

 the character of the jointing, the " onion structure," and the 

 zones of shearing together with certain large systems of joints, 

 standing at right angles to each other, resulting from pressure. 

 Microscopic examination shows that the granite consists of 

 microcline and orthoclase, plagioclase in very small amounts, 

 quartz, biotite and muscovite, with occasional ciystals of apa- 

 tite and magnetite and rarely pyrite. Variations in the shade 

 of the marketable granite, from very light to very dark gray, 

 are due to the relative amount of biotite which it contains. 

 The rock is of medium grain and its constituent minerals are 

 but slightly weathered. Pegmatitic offshoots, traceable directly 

 to the granite mass, were recorded by Mr. Finlay, and their dy- 

 namic effects on the enclosing schist were illustrated. The 

 contact metamorphism of the schist is inconsiderable. It is 

 chiefly shown in the greater abundance of biotite and quartz in 

 the immediate vicinity of the granite. Two dikes of augite- 

 camptonite were found ; one in the granite, the other in the 

 country-rock. They are noticeable for the manner in which 

 they have weathered. At times sixteen successive shells may 



