yiS REVIEWS 



large scale and in slides. Most of this took place prior to the formation of the ore 

 deposits, and the ore prevailingly occurs as a cement for the brecciated rock-fragments 

 and along shearing planes. All the rock is now more or less altered ; and the more 

 complete the alteration of the rock, the more complete has been its replacement by- 

 ore. Pyrrhotite occurs, it is true, as an original constituent of the norite, but the 

 amount of this original pyrrhotite is very small. The abrupt change from massive 

 sulphides to barren rock, the angular form of the included rock fragments, and the 

 comparative freedom from sulphides of these fragments are further adduced in support 

 of the theory that the ore deposits are essentially and predominantly secondary. 

 Fluker, W. H. "Gold Mining in McDuffie County, Georgia." Trans. 



Am. Inst. Min. Eng., Vol. XXXII; also in Ettg. and Min. Jour., Vol. 

 LXXIII, pp. 725, 726. 



Of particular interest as describing a Georgia gold-mining district never before 

 discussed in print, and far to the southeast of what is commonly considered the 

 Georgia gold region. The veins carrying the auriferous pyrite are of the usual 

 Appalachian type — stringers usually parallel to the lamination of the inclosing mica 

 and hydromica schists. 



Hill, B. F. The Terlingua Quicksilver Deposits, Brewster County \Texas\. 



Bull. 4, Univ. of Texas Mineral Survey. 8vo, pp. 74. 



The rocks in the vicinity of the Brewster county quicksilver deposits are marine 

 sediments representing the Lower and Upper Cretaceous and the Tertiary, with igneous 

 rocks of late Tertiary age. The ores occur in the Cretaceous beds occupying fissures, 

 either vertical or along bedding planes, marked by little or no displacement ; and 

 fault fissures marked by displacement with or without brecciated zones. Ore deposi- 

 tion in the district is supposed to have been due to the stimulus of the late Tertiary 

 intrusions and flows. The common ores are cinnabar and native mercury, though 

 other mercury ores occur in small quantity. The chief gangue material is calcite ; 

 aragonite and gypsum being next in importance. 



McCallie, S. W. "The Ducktown Copper Mining District." Eng. and 



Min. Journ., Vol. LXXIV, pp. 439, 440. 



Description of the geography, areal geology, and ore deposits of the Ducktown 

 district of southeastern Tennessee and its extension into northern Georgia. The 

 original contribution of greatest interest in this paper is the determination of the 

 occurrence of sheared igneous rocks in the vicinity of the ore bodies, a dark gray 

 quartz diorite occurring in linear areas parallel with the trend of the ore deposits. 



Pratt, ]. H. "Gold Mining in the Southern Appalachians." Eng. a7id 



Min. Journ., Vol. LXXIV, pp. 241, 242. 



Summary of recent gold-mining developments in Virginia, North Carolina, South 

 Carolina, Alabama, and Tennessee. 



Spurr, J. E. " The Original Source of the Lake Superior Iron Ores." 

 American Geologist, Vol. XXIX, pp. 335-49. 



The author points out that, though Van Hise and Leith agree with him in consider- 

 ing the original source of the Mesabi ores to be a green hydrous ferrous silicate of 

 organic origin, they refuse to call this material glauconite, because of its low content 

 or entire lack of potash. Spurr gives analyses and descriptions of undoubted glau- 

 conites from various localities, comparing these with the Mesabi material. He decides 

 that, though the Mesabi silicate carries less potash (0.31 per cent, and 0.41 per cent.) 



