474 WARREN AND POAVERS DIAMOND HILIr-CUMBERLAND DISTRICT 



was subsequently exploited for copper, silver, and gold, but has for some 

 time been abandoned. It is claimed that two carloads of picked ore run- 

 ning some 9 per cent iii copper and with small values in silver and gold 

 were at one time shipped from the vein. It is exposed for 380 feet and 

 attains a width of 12 feet. Its strike is north 6 degrees west, dip 45 

 degrees west. There are a number of smaller veins in the immediate 

 vicinity. 



The vein cuts the Joes Rock granite and an inclusion of the pre-Cam- 

 brian schist has been encountered in the mining operations. The Car- 

 boniferous conglomerate has also been found near the vein. This indi- 

 cates that the present surface of the land at this point was also the Middle 

 Carboniferous land surface invaded by the sea wliich deposited the Wani- 

 sutta conglomerates. The highly weathered character of the granite and 

 of the schist inclusion support this view. The composition of the red 

 Carboniferous sediment at its contact with the granite shows that the 

 former was a residual deposit derived from the latter. The quartz vein 

 coming in after the deposition and consolidation of the Carboniferous 

 sediments has a very fresh appearance, forming a marked contrast to the 

 deeply weathered and altered granite and green schist. 



The vein has been opened at several points, in One place by a shaft 100 

 feet deep, and its character is well exposed for observation. The quartz 

 is, where not stained by oxidation of the iron-bearing sulphides, of the 

 milky white variety, is distinctly banded, and often shows comb struc- 

 tures with small vugs. A number of minerals are found in the quartz, 

 either as scattered crystals or as small veins between the layers of quartz. 

 Pyrite is the most abundant mineral, with chalcopyrite next. Sphalerite, 

 galena, pyrrhotite, tetrahedrite, siderite, limonite, and turgite have been 

 noted. Small cross-cutting veins of chalcopyrite and galena occur. Al- 

 though fabulous values in silver have been reported, an assay made on a 

 carefully taken sample^® showed only 40 cents in silver and a trace of 

 gold. 



A similar quartz vein 2 miles east of Sheldonville, cutting the same 

 biotite granite, has been exploited for gold and silver. These and many 

 of the other smaller veins of quite similar general characteristics are all 

 referred to the same period of silica deposition as the Diamond Hill 

 quartz lode. 



rOST-PERMIAX DIABASE DIKES 



In the area discussed in this paper there are a few diabase dikes, some 

 of which are the youngest rock in the region. Such dikes are frequent in 



*• Lord and Gregory : Unpublished thesis In mining engineering. Mass. Inst. Tech- 

 nology, 1909. 



