abstracts: geology . 129 



In this report an attempt is made to estimate the quantity of ground 

 water available for irrigation within the area, based on the annual 

 fluctuation of the water table and the porosity of the materials as 

 shown by the logs of wells within the area. The results concerning 

 porosit}^ are checked against a pumping test made at the Lower Gorge 

 by the Bsiy Cities Water Company in which records were kept of the 

 quantity of water pumped, the area over which the water table was 

 lowered as a result of pumping, and the amount of lowering. A further 

 check is made by the use of stream-flow data, which show the amount 

 of water lost by Coyote River through percolation during a four-year 

 period, 1903 to 1907. W. 0. C. 



GEOLOGY. — Titi resources of the Kings Mountain district, North 



Carolina and South Carolina. Arthur Keith and D. B. Ster- 



RETT. U. S. Geological Survey Bulletin 660-D. Pp. 24, with 



maps, sections, and illustrations. 1917. 



The Kings Mountain district contains both metamorphic and igneous 



rocks, and the metamorphic rocks include some of sedimentary and 



some of igneous origin. In age the rocks range from Archean to 



Triassic. The formations that are associated with the tin deposits are 



the Carolina gneiss and a Roan gneiss, of Archean age; the Bessemer 



granite, of pre-Cambrian age; the Whiteside granite; and, especially, 



tin-bearing pegmatites of late Paleozoic age. • 



The pegmatite occurs in sheets, lenses, and irregular masses ranging 

 in thickness from a few inches to manj' j^ards and attaining half a 

 mile in length. The tin-bearing deposits occur in pegmatite masses 

 within Archean rocks, either the Roan gneiss or the Carolina gneiss 

 along or near its contact with the Roan gneiss. The cassiterite appears 

 to have been one of the first minerals in the pegmatite to crystallize, 

 and it seems clear that the cassiterite was an original constituent of 

 the pegmatite. • R. W. Stone. 



GEOLOGY. — Zinc carbonate and related copper carbonate ores at Ophir, 

 Utah. G. F. LouGHLiN. U. S. Geological Survey Bulletin 

 690-A. Pp. 14, with illustrations. 1917. 

 This paper calls attention to the marked lamellar structure of the 

 zinc carbonate, the prevailing absence of calamine, and the intimate asso- 

 ciation of the zinc carbonate with copper carbonates in the Ophir mining 

 district. The processes of deposition of the carbonates are described 

 and the following conclusions of economic importance are reached: 

 It is to be expected that bodies of lamellar zinc carbonate like those 



