Geology and Mineralogy. 293 



Press). — This book is designed to present an accurate account of 

 the present state of opinion regarding the genesis of ores. The 

 different chapters have been written by men each of whom is an 

 authority concerning the type of deposit that he describes. Many 

 of the papers have appeared previously in various magazines, etc. 

 The following list of chapter subjects with their authors is suffi- 

 cient proof of the character and value of the volume : Introduc- 

 tion by H. Foster Bain ; The Clinton Type of Iron Ore Deposits 

 by C. H. Smyth, Jr. ; The Lake Superior Type of Iron Ore 

 Deposits by C. K. Leith ; Flats and Pitches of the Wiscon- 

 sin Lead and Zinc District by H. Foster Bain ; Lead and Zinc 

 Deposits of the Ozark Region by E. R. Buckley ; Native Copper 

 Deposits by Alfred C. Lane ; Cobalt District, Ontario, by S. F. 

 Emmons ; Geology at Treadwell Mines by Oscar F. Hershey ; 

 The Saddle Reef by T. A. Rickard ; Contact Deposits by James 

 F. Kemp ; The Conglomerates of the Witwatersrand by F. H. 

 Hatch ; Replacement Orebodies and the Criteria by Means of 

 which they may be Recognized by J. D. Irving; Outc-rop of Ore- 

 bodies by William H. Emmons ; Some Causes of Ore-Shoots by 

 R. A. F. Penrose, Jr. w. e. f. 



12. Brief Notices of^ some Recently Described Minerals. — 

 Muthmannite is a telluride of gold and silver from Nagyag in 

 Transylvania. The mineral has been earlier called miillerine, gelb- 

 erz and weistellur and by Schrauf was referred to krennerite 

 (see Dana, Syst. Min., p. 104). Zambonini, however, makes it 

 distinct with the formula (Ag, Au) Te ; this is based upon the 

 following analysis by C. Gastaldi : Te 46*44 Au 22*90 Ag 26*36 

 Pb 2*58 = 98*28. The name is given in honor of W. Muthmann 

 of Munich. — Zeitschr. Kryst., xxix, 246, 1911. 



Yttrofluorite is a fluoride of calcium and the yttrium earths 

 described by Th. Vogt from a pegmatite in northern Norway. 

 It resembles fluorite in form but shows only imperfect octahedral 

 cleavage. The luster is vitreous ; the color yellow to brown or 

 green ; hardness = 4*5 ; specific gravity 3*56. An analysis gave : 



F CaO Y-earths Ce-earths alk. ign. 



45*54 54*89 17*35 1*68 0*15 0*67 H 2 under 100° 



0*22 = 120*50, or deducting O 19*17 = 101*33. 



Yttrofluorite is near yttrocerite but differs in its larger percent- 

 age of the yttrium-earths and practical absence of water. — Cen- 

 tralbl. Min., 1911, 373. 



Eichbergite is a sulphide of copper, iron, antimony and bis- 

 muth from the magnesite deposits of Eichberg in the Semmering, 

 Austria ; it is described by O. Grosspietsch. It occurs in massive 

 form with indistinct crystalline structure. The color is iron-gray; 

 luster metallic ; hardness over 6 ; specific gravity 5*36. An analy- 

 sis gave : 



S Bi Sb Cu Fe 



12*74 51*53 30-00 3*62 1*45 = 99*34 



The calculated formula is (Cu,Fe) 2 S.3(Bi,Sb) 2 S 3 .— Centralbl. 

 Min., x, 1911, 434. 



