650 REVIEWS 



Veins barren of silver are widely scattered throughout the southern 

 part of the state and include most of the deposits examined. They are 

 most common in Tertiary lavas. The ore-shoots vary greatly in size. 

 The ore consists of oxides derived from the weathering of vein material, 

 hence its depth depends largely on the permeabiHty of the rock to 

 circulating water. The ore minerals are psilomelane, pyrolusite, and 

 manganite; these are accompanied by barite, calcite, and iron oxide. 



Bedded deposits vary as to character and associated rocks. They 

 may be contained in tuffs, or they may be the result of replacement of 

 sandstone. They are generally of Tertiary age. Such deposits do not 

 extend to great depths and are worked through shallow pits and shafts. 

 The manganese minerals are psilomelane, pyrolusite, manganite, and sub- 

 ordinately braunite. Quartz, feldspar, iron ores, and calcite are the chief 

 gangue minerals — partly secondary, partly the unreplaced minerals of 

 the rock. Much of this ore, developed in sandstones and only partially 

 replacing the country rock, is siliceous. 



Manganese ore associated with travertine is known from one locality 

 only; here the travertine and the clayey manganese-bearing beds are 

 capped by basalt. The manganese mineral is principally botryoidal 

 and vesicular psilomelane. 



A detailed description of the geography, geology, and manganese 

 deposits of each of the districts is given; for these the reader is referred 

 directly to the carefully prepared paper itself. 



C. H. B., Jr. 



World Atlas of Commercial Geology; Part I, Distribution of Mineral 

 Production. United States Geological Survey, 1921. Pp. 72, 

 pis. 72. 



The purpose of this atlas, prepared by more than a score of geologists, 

 is "to set forth graphically and to describe concisely the basic facts 

 concerning both the present and the future sources of the useful 

 minerals." Part I deals chiefly with present sources; later parts will 

 exhibit, so far as practicable, the mineral reserves of the world. The 

 maps of Part I, which deal with the most important thirty mineral 

 commodities, are arranged in groups of eight, each group containing (i) 

 a map of the world showing production and, for major commodities, 

 consumption by countries in 1913, the last year of normal production; 



(2) a map of each of the continents, indicating production by countries, 

 districts, or fields, in percentages of the world's production in 1913; and 



(3) a map of the United States, exhibiting production in 1918 by states, 

 districts, or fields, in percentages of the total output of the country. 



