PEGMATITE D IKES CONTAINIXG EAKE MINERALS. 325 



Here the schists liave been worn away I'roiii the main dike, whicli 

 stands np in a vertical wall 33 feet high. In many places a veneering- 

 of schist remains attached, and when it is removed the impression of the 

 schist is sharp and clear on the surface of the pegmatite. The layer of 

 schist against which the pegmatite rests shows no signs of its influence, thus 

 differing from the schist in contact with the all)itic granite at the Barrus 

 farm, descriVjed below, where the contact metanior])liism is pronounced 

 and the granite and schist are fused together. 



The secondary vein, as described above, is seen high np on the face of 

 the vertical side of the main dike, and seems to me to have been deposited 

 in a vertical transverse fissure in the latter, whicli fissure extends from the 

 east face only about halfway across the dike and to an intermediate 

 distance up and down. This fissure seems to have been formed in the 

 newly consolidated pegmatite and to have been filled by a magma of 

 peculiar comj)Osition, much hydrated, rather than by a simple solution. 

 Thus, commencing with this tonalite and ending with the quartz veins, I 

 suppose there is an unbroken series from igneous fusion to aqueous solution. 



At Chesterfield Hollow the granite of the main vein is of the usual character, 

 but shows uo berj'l and little mica. The successive deposition of minerals in the 

 .secondary vein is, first, orthoclasc in huge crystals, large plates of muscovite, some- 

 times 6 to 10 inches in diameter, and grayish-white quartz. Within this comes an 

 irregular mass of a coarse albitic granite, with green muscovite, spodumeue. 

 greenish-white beryl in masses sometimes 10 to 2~) pounds in weight, and a zircon 

 rich in uranium in minute double pyramids rarely three-sixteenths of an inch in 

 diameter. Usually this albitic granite passes gradually into a mixture of quartz 

 and cleavelandite iu bunches of snow white plates inclosing less muscovite — 

 manganese garnets in large and abundant but imperfectly crystalline grains, 

 zircon, spodumene, and yellowish-white beryl in irregular mas.ses. 



Finally the core of the vein consists of an irregular sheet of smoky quartz, 

 penetrated by long prisms of spodumene, green beryl in small and good crystals, 

 muscovite iu hexagonal plates, often well cry.stallized and up to 2 or 3 inches across, 

 as well as in sheets, scattered scales and wavy films which in part seem to be altered 

 to margarodite, columbite, and zircon iu rare but perfect crystals. This succession 

 of minerals in the secondary vein is not as regular as might be inferred from the 

 foregoing description, in which it is intended to indicate only the general tendency 

 toward a definite arrangement. 



At Walnut Hill, in Huntington, the material of the main vein is similar to 

 that of the i)receding locality. In the secondary vein the rich deposit was found 

 to be a very coarse albitic granite, rich in black tourmaline in huge masses, mus 

 covite, and garnet; then followed cleavelandite, white quartz, and spodumene in the 



