670 The American Naturalist. [July, 
The axial ratio, recalculated from von Rath's measurement, is a : 2: c= 
en i Fea ia 3 A=69° 35°. New measurements by Busz gave 
Pr 396 * PET EN ar Kobellite, from the 
oo abes 1 Mine, en, Colorado, has been analyzed by Kellar. Its 
composition is: 
"S B -S0 Ph Ag Cu Fe Zn Gange 
18.39 28.40 7.55 36.16 3.31 2.59 1.50 .39 45, 
which may be represented by z(Pb.Ag,Cu,) S.(BiSb),S, It differs 
‘in composition from the mineral called kobellite by Rammelsberg 
(Pb,BiSb,), but is like that to which the name was first given by Sel- 
terberg. The same author suggests the name ///anite for a substance 
of the composition 3(PbAg,) Bi,S, described by himself!! several 
years ago. JVivemife is a rare mineral associated with fergusonite 
and gummite at the gadolinite locality in Llano County, Texas. It 
is described by Genth as velvety black, with a brownish streak. It 
is easily soluble in nitric acid, and possesses the composition : 
HU .UO IhO, Y,O, etc FeO, PbO Ign Ins SpGr 
46.75 19.89 7.57 11.22 .58 16.105 253 142 201 
It is allied to bróggerite (3RO.UO,) and cleveite (6RO.2UO,.3H,0) 
in containing a large proportion of uranium. Its hardness is 5.5, 
and its composition is represented by (gRO.4UO,.3H,O). Two 
varieties of fergusonife have been found in the same locality. The 
first corresponds to Cb,O,.R,0,.H,O, and the second to Cb,O,. R,O,. 
3H,O. The two are tlocely associated. The first is ptobebly tetra- 
gonal, with a bronzy lustre on a fresh fracture. It is infusible, 
decrepitates when heated, and changes to an olive green color. The 
second variety is deep brown in color. Its streak is greenish gray. 
Upon ignition it turns light brown but does not decrepitate. 
Hydrocerussite (2PbO, + Pb(OH,) corresponding to azurite 
among the copper salts, has been produced by Bourgeois, ? by acting 
upon lead acetate with ammonium carbonate. The little crystals thus 
formed have all the properties of the natural substance. By means of 
them the composition of the mineral has been determined. The white 
lead of commerce is found by the author to be a mixture of two sub- 
stances with the composition respectively of cerussite and hydrocerus- 
site. Percylite and caracolite are briefly mentioned by Fletcher ™ 
10 Zeits. f. Kryst., 1889, XVII., p. 67. 
V Jour, Amer. Chem. Soc., Vol. VIL, No. 7. 
~ Amer. ji P. 474- 
Min. Magazine, 1889, P. $»n. 
