360 proceedings: geological society 



ing abundant pyrrhotite. A statistical review of a number of ore depos- 

 its classified with respect to the mineral composition of the primary ore 

 appears to lend some support to this hypothesis, since chalcocite zones 

 in ores containing abundant pyrrhotite are generally limited vertically 

 while those containing sphalerite pyrite, and chalcopyrite extend to 

 greater depths. 



The 255th meeting was held in the Cosmos Club March 27, 1912, with 

 President Stanton in the chair. 



REGULAR PROGRAM 



An occurrence of emeralds in North Carolina: D. B. Sterrett. Emer- 

 alds are found in several types of deposits. In Columbia they occur in 

 calcite veins in bituminous limestone; in Upper Egypt and in the Ural 

 Mountains, . in dark mica schist interfoliated with talc schist; in the 

 Salzburg Alps, in a greenish-brown mica schist interbedded with chlo- 

 rite and hornblende schist; in Maine, Connecticut, and on Crabtree 

 Mountain, Mitchell County, North Carolina, in pegmatite; at Hiddenite 

 in Alexander County, North Carolina in cavities in veins cutting biotite 

 gneiss, associated with quartz, calcite, dolomite, muscovite, rutile, black 

 tourmaline, pyrite, monazite, and hiddenite. 



At a new locality in Cleveland County, North Carolina, 4f miles 

 S.30°W. of Shelby, emeralds occur in pegmatite cutting hornblende 

 hypersthenite and olivine gabbro. Some of the hypersthenite contains 

 olivine and grades into gabbro. The two rocks are probably genetically 

 related. Both have been intruded and surrounded by biotite granite. 

 The granite has acted on the basic rock both absorbing and altering the 

 composition of part to less basic variety. Pegmatite, probably geneti- 

 cally associated with the granite, has rilled fissures in the basic rocks. 

 In one of these pegmatites emeralds have been found. It is suggested 

 that the agencies which formed the pegmatite contained the necessary 

 elements of the formation of beryl. The absorption of some of the basic 

 rock by the granite magma supplied the oxide of chromium necessary to 

 impart an emerald green color to the beryl. Analyses by Dr. R. C. 

 Wells, of the Geological Survey, showed the presence of 0.16 per cent 

 ( !r 2 3 in the hornblende hypersthenite and of 0.17 per cent in the olivine 

 gabbro. This is practically the same percentage of oxide of chromium 

 contained in emerald. Beryl found in other pegmatites inclosed in 

 granite and mica gneiss in this region are pale aquamarine green, yellow- 

 ish, or white. 



Some emeralds of fine color have been found at the new locality. 

 The best one was found on the surface in a cotton field. It is about half 

 of a crystal, split parallel with its length, and measures about 1 by f by 

 \ inch. The color is a fine deep green. About a quart of emeralds 

 have been found in all and the color and quality of these are about equal 

 to the average emeralds from Columbia. The best gem so far cut from 

 this North Carolina locality weighs 0.83 carats and has been valued at 



