Genth and Vom Rath. *^^^ [April 17, 



and implanted in calcite. Minute very brilliant columbine-red or cherry- 

 red crystals of descloizite are implanted in, or crystallized upon the vana- 

 dlnite and calcite, and may have been formed from constituents of decom- 

 posed or dissolved vanadinite. Analysis bl. 



2. Other varieties of vanadinite are associated with the black or dark- 

 brown descloizite. They all show the hexagonal prism and the basal 

 plane, and most of the crystals the pyramid also ; a more acute pyramid, 

 and a prism and pyramid of the second order are rarely indicated. The 

 planes ar.e generally smooth and brilliant, but there are some, in which the 

 basal plane is rough, as if corroded, but surrounded by a smooth and 

 brilliant margin. The crystals vary in size from 1.5 to 3"" in length and 

 0.5 to 2™" in thickness. Their color is from orange-yellow to brownish- 

 orange. 



They are mostly of a more recent origin than the brown descloizite which 

 they accompany ; it appears, however, that the latter was still growing 

 when this vanadinite and iodyrite were formed, since the large crystals 

 of descloizite are frequently pitted by tlieir impressions ; the vanadinite 

 and iodyrite seem to have crystallized simultaneously, but there are smaller 

 crystals of descloizite of a red color of a more recent origin ; they are 

 attached to iodyrite, vanadinite and calcite. 



Analyses : 



a. As not enough of the pure mineral from the Sierra Bella could be 

 obtained, an indefinite quantity of the incrustations upon wad was purified 

 as much as possible by washing off the lighter particles and analyzed- 

 It gave : 0.0153 grm Ag = 0.0050 grm CI, 0.2261 grm PbSO^, 0.0007 grm 

 Mg.As^O,, 0.0021 grm MgjP.p, and 0.03(34 grm V.Pj. 



bl. 1 grm gave : 0.0757 grm Ag — 0.0249 grm Ci, 1.0647 grm PbSO^, 

 and 0.1814 grm ( VP)205 ; 1.5665 grm, after deducting 0.0008 grm quartz or 

 1 .5657 grm pure vanadinite gave : 1.G669 grm PbSO^, 0.0282 grm Mg.^AsgO,, 

 0.0095 grm Mg^P.p^ and 0.2779 grm VjOj. These quantities give the 

 following percentage : 



Less O, 100.26 



Equiv, to CI. = 0.55 



99.71 

 The analysis bl corresponds exactly to the formula Pb^Cl [(VAsP)04]3 in 

 which a small portion ot the vaoadiiim is replaced by arsenic and phos- 

 phorus, while analysis a shows a slight excess of lead which is probably 

 present a;* cerussite. 



