Genth.] «^" [March 18, 



II. Vanadinite and Descloizite, 



a. Mr. Cliarles R. Fletcher, of Boston, formerly Superintendent of the 

 Mammoth Gold mine, ne.ar Oracle, Pinal county, Arizona, sent me .about 

 two years iigo a liiirlily interesting and fine variety of vanadinite and des- 

 cloizite and sulipociuently, from a new occurrence, he presented me with a 

 number of magnificent specimens of tlie same minerals, which, as for 

 vanadiniic. are some of the finest which I have seen, for all of which I am 

 greatly indebted to him. 



Of the first lot received I sent a small piece to Prof. G. Tom Il'Uli, who 

 describes it [1. c.) as being composed of barrel shaped crystals with a 

 brown nucleus, surrounded by a yellow coating of very fine aggregations 

 of more recent growth, the druses and surfaces covered with exceedingly 

 minute crystals of descloizite. 



The vanadinite from Ibis mine occurs upon quartz in crystals, varying 

 in size from 0.1"™ to 8™™ in length, the smallest crj'slals are of a yellow 

 color, whi« h changes with their size incntasing to an orange yellow, orange 

 red, aurora red to a brownish-red, often variegated. Perfect isolated crystals 

 are rare and generally small, they are mostly united to clusters and crys- 

 talline coalings upon the quartz; the crystals are often very much dis- 

 torted and eav(;rnous. The forms which I have been able to distinguish 

 are the hexagonal prism with pyramid and basal plane, the latter fre- 

 quently very .«-mall or entirely wanting. 



Calcite sometiines surrounds the vanadinite and is again covered by 

 vanadinite crystals. 



b. A brownish-black and black descloizite from this locality covers in 

 form of H cryst.alline coaling in minute rhombic pyramids the rcddish-white 

 massive gold quartz, or is united to clusters of microscopic crystals upon 

 and between the crystallized quartz. Upon these coatings of descloizite 

 are the crystals of vanadinite, whicii again are covered with exceedingly 

 minute crystals of descloizite. The yellow crystalline coating upon the 

 brown nucleus, mentioned by vom Raih has often 7io nucleus of vanadin- 

 ite, it is dull and of a yellow color Ihronghout the mass of the hexago- 

 nal barrel sliaped crystals. Mr. fl. F. Keller, who analyzed the brown 

 and tiie bri-lit orange red crystals from this locality (a, 1 and 2) found that 

 the yellow mineral contains no chlorine. It is very probable therefore 

 that the dull yellow crystals are pseudomorphs of descloizite after vana- 

 dinite. 



Not enough of the descloizite could be obtained for analysis, qualitative 

 tests however gave lead, zinc and traces of copper and manganese oxides 

 with vanadium penloxide. 



c. A ]ieciiliar variety of vanadinite, much resembling pyromorphife, has 

 been noticed in Yavapai county, Arizona, by Mr. J. C. Cooper, of To- 

 peka, Kansas, who has sent specimens to the East. Mr. Clarence S. 

 Bement kindly prcsenled to me one, of which I have made the analysis 



