Gentli and Vom Rath.] Oi'± [April 17, 



0.14G9 grin ZaO, 0.0301 grm MnoO^, 0.0038 grm Fe.fi^, 0.2269 grm V.,05 

 less 0.0086 grm for vanadinite, and 0.0033 grm Ag = 0.0011 grm CI = 

 0.0442 grm vanadinite. P2O5 and AS2O5, on account of their small quan. 

 tity, were determined from the material of c2 and c3 and, afier the deduc- 

 tion of the foreiga substances, 2.0498 grm descloizite gave 0.0131 grm 

 Mg.AsjOj and 0.0015 grm Mg^PjO-. 



c3. Another portion of the same crystals was ignited strongly in a pla- 

 tinum crucible. 1.1560 grm gave a loss of O.O0I8 grm. The mineral was 

 fused to a black slag and the crucible badly injured. The fused mass was 

 dissolved with difficuly in dilute nitric acid and gave 0.0018 grm Si02, but 

 contained no higher oxides of manganese. Taking the analysis cb as 

 the basis for the subtraction of the impurities 0.0736 grm is obtained 

 for MnO^ and 0.0039 grm for Fe^Oa, giving for the vanadates 1.0767 grm 

 less 0.0450 grm vanadinite or 1.0317 grm descloizite. 0.0736 grm pyro- 

 lusite has lost by strong ignition 0.0135 grm oxygen which, subtracted 

 from 0.0518 grm loss by ignition, leaves 0.0383 grm for water. The 

 analysis gave : 0.8444 grm PbSO^, less 0.0478 grm for vanadinite or 0.7966 

 grm, 0.0074 grm CuO, 0.1365 grm ZnO, 0.0241 grm MnjO^, 0.0034 grm 

 FeA and 0.2312, less 0.0092 grm for vanadinite or 0.2220 grm VA- 



The analyses of the blackish-brown descloizite gave, therefore, as fol- 

 lows : 



cl c2 c3 Mean. Atomic ratio. 



Sp. Grav.==: 5.882 — 5.814— 



PbO = 55.73 — 56.53 — 56.82 — 56.36 = 0.252 =2.12 



CuO = 0.85 — 1.05 — 0.70 — 0.87 = 0.011 1 



ZnO — 13.95— 14.56 — 13.23 — 13.91 r= 0.172 



MnO = 3.21 — 2.77 — 2.23 — 2.74 = 0.039 



FeO = 0.27 — 0.34 — 0.30 — 0.30 = 0.004 



AsA = 0.53 — 0.48 — 0.48 — 0.50 = 0.002 ^ 



P2O5 = trace— 0.04— 0.04- 0.04= [==0.119 = 1. 



VA = 20.89 — 21.63 — 21.52 — 21,35 = 0.117 J 



H,0 = 3.07 —not det.— 3.71— 3.39 = 0.189 =1.59 



= 0.226 = 1.90 



98.50 99.03 — 99.46 



The analyses of the dark descloizites, after the subtraction of their admix- 

 tures gave approximations, agreeing very closely with the analyses of the 

 best and purest red varieties. Both contain equal atoms of lead and zinc, 

 the latter, in part, replaced by the isomorphous metals manganese, iron, 

 and copper, the dark varieties containing a smaller quantity of zinc and a 

 correspondingly higher of manganese. A very small quantity of the vana- 

 dium is substituted by arsenic and phosphorus. In the red crystals the 

 hydrogen is about in the same ratio as vanadium, while the dark varieties 

 contain more of the former, but as there is an uncertainty whether some 

 of the evident admixtures do not contain water, not too much importance 



