proceedings: gkological socmTY 385 



the region ranging from schist and granite of pre-Cambrian age to 

 basalt and conglomerate of Quaternary age, and the replacement de- 

 posits are in sandstone and tuff beds of Tertiary age. The ores con- 

 sist of the oxides psilomelane, pyrolusite, manganite, and wad. Cal- 

 cite generally accompanies the manganese oxides, and iron oxides, 

 barites, and gypsum occur in some of the deposits. Quartz does not 

 occur except as a constituent of rock fragments inclosed in the veins 

 and as unreplaced grains of the sandstone. The source of the man- 

 ganese oxides is obscure but in some of the deposits the manganese 

 oxides are believed to have been derived from the decomposition of 

 manganiferous minerals in overlying rocks and deposits by meteoric 

 waters. In other deposits the ore bodies may be residual from man- 

 ganiferous calcite deposited by rising hot solutions in the fissures. 



J. T. Pardee: Manganese deposits of the Northwestern States. — 

 At Butte, Montana, lodes formed along steeply pitching fractures in 

 granite are characterized by manganese minerals in a zone peripheral 

 to the central copper zone. The arrangement of these zones suggests 

 a central deep source from which the metals were carried upward and 

 outward. Rhodochrosite, the carbonate of manganese, forms work- 

 able bodies from which more than 60,000 tons of ore were mined in 

 1 91 8. At Philipsburg, Montana, lodes cut Paleozoic limestone and 

 intrusive granite. In the limestone near the granite, large irregular 

 chambers filled with manganese oxides are found along the lodes. 

 During 191 8 and 191 9 they yielded more than 200,000 tons of high 

 grade ore. The manganese oxides are derived from the oxidation of 

 rhodochrosite which was introduced during a late phase of the lode 

 mineralization. Small deposits of the same origin as those at Butte 

 and Philipsburg occur in the Tintic and Erickson districts, Utah; 

 the Siegel and Ely districts, Nevada; Pleasant Valley, Oregon; and 

 Omak, Washington. 



Deposits at several other places belong to a class whose manganese 

 was derived from more or less disseminated or obscure sources. The 

 extensive deposits in the Olympic mountains of Washington are possi- 

 bly of sedimentary origin though they have been greatly modified by 

 regional metamorphism. The deposits near Green River, Utah, were 

 concentrated during the weathering of a manganese-bearing Hme- 

 stone bed in the McElmo formation. 



E. F. Burchard: Managanese-ore deposits of Cuba.- — Manganese 

 ore is found in Cuba, in Oriente, Santa Clara, and Pinar del Rio Pro- 

 vinces, but in Oriente Province only does it occur in large commercial 

 quantities. In Oriente the important deposits are in two areas, one 

 north of Santiago de Cuba, the other south of Bayamo. 



The manganese ore of Oriente occurs in proximity to areas of vol- 

 canic rock, but the deposits of the other two provinces, which are small 

 and unimportant, are remote from volcanic areas. The ore is found 

 in the oxidized zone, mainly near the surface, but in places extends be 

 low groundwater level. The deposits are in sedimentary rocks of 



