1048 The American Naturalist. [December, 
name is in honor of Mr. Maynard Bixby of Salt Lake City, who first 
, brought the mineral to notice 
Associated with the bixbyite are topaz crystals showing combinations 
of the following forms: 
E IVUS 6, OUIS 8,110; T, 1207 ¢, ZOls £021; y OTI; 0, 221 3 u, 
111. 
There are also rough pseudomorph crystals, probably after the man- 
ganese garnet, spessartine, now composed of a mixture of bixbyite with 
either topaz or quartz or botb. 
Zinkenite Group.—Spencer® describes a twin crystal of chalcos- 
tibite (wolfsbergite) from Wolfsberg with 102 as twin plane, not before 
observed. Also (rare) simple crystals of zinkenite from the same place 
showing the new form 001. He then shows that by a proper orienta- 
tion of the crystals of these two minerals the similarity in habit, stria- 
tion, and twinning may be shown and also their place in the isomorphic 
zinkenite group as follows: 
i ee Fe 
Zinkenite . . PbS.Sb,S, 0.5575: 1: 0.6353 
Wolfsburgite Cu,S.Sb,S, 0.5312: 1 : 0.6376 
(Chalcostibite, Penfield) 0.5312 : 1 : 0.63955 
Sartorite PbS.As,S, 0.5389 :1 :0.6188 
Emplectite Cu,S.Bi,S, 0.5430 : 1 :0.6256 
He states on the ground of crystallographic measurements that prob- 
ably the mineral guejarite described by Cumenge as having the com- 
position Cu, S.2Sb,S, will be found to be identical with chalcostibite. 
This has been proved by Penfield and Frenzel’ by a re examination of 
material from Guejar and a study of new material from Huanchaca, 
Bolivia, supposed to be guejarite. Measurements of crystals from these 
two localities gave results entirely agreeing wlth those from typical 
chalcostibite from Wolfsburg. The chemical constitution of the 
minerals from the three localities was also shown to be identical, and 
to satisfy the chalcostibite formula: Cu,S.Sb,S,._ On the chaleostibite 
from Huanchaca Penfield observed 20 forms of which 13 were new as 
follows: 130, 209, 207, 205, 203, 302, 065, 136, 133, 265, 263, 261, 
4.12.5. He also shows that the forms observed by Laspeyres, 7.14.8, 
and 7.21.27, should be 6.12.7, and 134 respectively. In Penfield’s 
paper is further a description by Spencer of a chaleostibite specimen’ 
_ Min. Mag., Vol XI, No. 52, p. 188. 
’ An. J. Sci., Vol. CLIV, 1897, p. 27. 
