43 S W. F. IliUebrand — Analyses of three Descloizites. 



In almost every respect this mineral resembles, so far as the 

 published descriptions allow of judging, the descloizite of 

 Penfield,* the cupro-descloizite of Rammelsberg,f and the 

 ramirite of de Leon,:}: perhaps also the tritochorite of Frenzel,§ 

 to the similarity of which with his variety of descloizite Pen- 

 field draws attention in his paper. Professor Genth's surmise 

 (1. c, p. 39) of the specific identity of all these substances 

 seems highly probable. Characteristic for the present variety 

 is the greater replacement of the lead-zinc vanadate — true 

 descloizite — by the isomorphous lead-copper vanadate, and the 

 lessened tendency toward a fibrous structure, which in the 

 other varieties described seems to be a decidedly pronounced 

 feature. Possibly this last characteristic of the Tombstone 

 mineral, if it be not accidental in view of the few specimens 

 (three) examined, is a condition of the first. 



According to Rammelsberg,| the lead-copper vanadate cor- 

 responding to the lead-zinc vanadate (descloizite) is mottramite 

 or psittacinite, though it seems not improbable that it may be 

 the chileite of Dana's Mineralogy, Domeyko's analyses,^" 

 which led Kenngott to ascribe the above name to the Chilian 

 mineral, show a deficiency of 2*5 and 2'8 per cent, which may 

 very well be V 2 5 . At all events, a recalculation of his 

 analyses based on this assumption leads to a proportion for 

 Pb6+ CuO : V 2 6 : H 2 of nearly 4:1:1. 



In view of the well defined character of all these highly 

 cupriferous varieties of descloizite it would be well to designate 

 them once for all by some distinctive name. Tritochorite 

 would have precedence if the substance to which that name 

 has been given is really identical with the others, but Ram- 

 melsberg's cupro-descloizite is more appropriate as indicating 

 at once the relationship to descloizite, and I would suggest 

 that it be henceforth used for all cupriferous descloizites show- 

 ing the physical characteristics of the mineral above described. 



Note. — Since the foregoing was written there has appeared in 

 the Bull. Soc. Franc. Min., Feb., 1889, p. 38, a paper by F. Pisani, 

 in which he gives another analysis of the Mexican cupro-descloizite 

 and discusses briefly the relations of various vanadates. The 

 essential identity of all the above enumerated cupriferous lead- 

 zinc vanadates, with the addition of another — schaffnerite — con- 

 cerning which I have been unable to find any further reference in 

 mineralogical literature, is therein upheld, and the suggestion of 

 Penfield's regarding the possible identity of tritochorite and 



* This Journal, III, xxvi, 361, 1883. 



f Monatsb. Berl. Acad., 1883, 1215. 



\ La Ramirita, nueva espece mineral, Mexico, 1885. 



§ Tschermak's Min. and Petr. Mitth., iii, 506,' 1880; iv, 97, 1881. 



I Chemische Natur der Mineralien, p. 32. 



\ Ann. d. Mines, IV, xiv, 150, 1848; Phil. Mag.. Ill, xxxiv, 395, 1849. 



