658 REPORT OF NATIONAL MUSEUM, 1897. 



forms tbe negative part. These throe elements combine in this manner 

 with most of the metals. Further, the three negative elements are 

 essentially isomorphous, and may replace each other in varying amounts. 

 These types are illustrated by the following specimens: 



Orpiincnt — Simshiiie mino, Sunshiue, Utah. (Cat. No. 84027, U.S.N. M.) 

 Molybdenite— Hallein, Austria. (Cat. No. 49904, U.S.N. M.) 

 Sphalcrito— Cumberland, England. (Cat. No. 4958i5, U.S.N.M.) 

 MilliTite — Gap mine, Lancaster County, Pennsylvania. (Cat. No. 48214, U.>S.N.M.) 

 Galena— .loplin, Missouri. (Cat. No. 51346, U.S.N.M.) 

 Covollite— Gray Rock mine, Ikttte, Montana. (Cat. No. 84071, U.S.N.M.) 

 Cinnabar— Idria, Spain. (Cat. No. 81728, U.S.N.M.) 

 Argentite — Guanajuato, Mexico. (Cat. No, 84057, U.S.N.M.) 

 Chalcooite— Cornwall, England. (Cat. No. 16981, U.S.N.M.) 

 Pyrrbotite— Asbe County, North Carolina. (Cat. No. 46236, U.S.N.M.) 

 Linna'ite — Mint^ La Motte, Missouri. (Cat. No. 45143, U.S.N.M.) 

 Pyrite— Central, Colorado. (Cat. No. 81844, U.S.N.M.) 



Cbalcopyrite — Gap mine, Lancaster County, Pennsylvania. (Cat. Nt). 48216, 

 U.S.N.M.) 



lioruite- Freiberg, Saxony. (Cat. No. 49473, U.S.N.M.) 



Tiemanuite- Marysvale, Utah, (Cat. No. 81821, U.S.N.M.) 



Henryite— Red cioud mine, (Jold Hill, Colorado. (Cat, No. 9705, U.S.N.M.) 



Sylvanite— Oftenbanya, Hungary. (Cat. No. 9719, U.S.N.M.) 



Arsenides antimonides, and Msmuthides. — Arsenic, antimony, and bis- 

 muth are analogous in their jjroperties, and unite with other elements to 

 form arsenides, antimonides, andbismuthides. Arsenic and antimony, 

 and, to a certain extent, bismuth, are essentially isomorphous, and may 

 replace one another in varying amounts. With the arsenides, antimo- 

 nides, and bismuthides are included the sulpharsenides, sulphantin)o- 

 nides, and sulphbismnthides — compounds in which the negative part is 

 taken by arsenic, antimony, or bismuth with sulphur. 



The following specimens are illustrative of these types: 



NiccolitL' — Gem mine. Silver Clitf, Colorado. (Cat. No. 51465, U.S.N.M.) 

 L()llingite — Horace Porter mine, Gunnison County, Colorado. (Cat. No. 51566, 

 U.S.N.M.) 

 Cobaltite— Coquimbo, Chile. (Cat. No. 13372, U.S.N.M.) 

 Arsenopyrite — Rockbridge County, Virginia. (Cat. No, 13982, U,S.N.M.) 



Sulphnnalts. — This class includes the various native salts of the sul- 

 phoacids of arsenic, antimony, bismuth, tin, and germanium. The ele- 

 ments })resent as bases are chiefly lead, copper, and silver; less often 

 iron, mercury, zinc, etc. The several compounds are arranged with 

 reference to their negative parts as follows : Sulpharsenites, suliihan- 

 timonites, and sulphbismuthites; sulpharsenates, sulphantimonates, 

 sulphstannates, and sulphgermanates. 



Examples of these are shown in the specimens of — 



Chalcostibite— St. Gertraad, Carinthia, Austria. (Cat. No. 84088, U.S.N.M. ) 

 Freieslebenite — Garfield mine, Gunnison Count j-, Colorado. (Cat. No. 82622, 

 U.S.N.M.) 



Pyrargyrite — Yankee Boy mine, Ouray, Colorado. (Cat. No. 81122, U.S.N.M.) 

 Tetrahedrite— Freiberg, Saxony. (Cat. No. 45656, U.S.N.M.) 

 Tennantite— Freiberg, Saxony. (Cat. No. 49486, U.S.N.M.) 



