APPENDIX. O 



The oxygen ratio of. R. fi and As is 3 '74 : 11 '07 : 19 - 16, or nearly 1:3:5, giving 1 the 

 formula (^ ft 3 + f S) As. in which a portion of the oxygen is replaced by fluorine. 



In the closed tribe blackens at a moderate temperature, but regains its color on cooling ; 

 at a higher heat fuses easily to a yellow glass and gives a faint white volatile sublimate, 

 etching the tube slightly. The same in the open tube, with evolution of acid fumes, red- 

 dening litmus paper. On charcoal, B. B. fuses readily and gives a white sublimate with a 

 strong arsenical odor in It. F. With soda and charcoal powder in a matrass yields a subli- 

 mate of metallic arsenic. "With the fluxes reacts for iron and manganese. In the forceps 

 fuses 1 at 2, giving an intense soda flame. Decomposed by sulphuric acid •with evolution of 

 fluohvdric acid. 



Found near Durango in Mexico. The chemical composition of this mineral places it 

 near amblygonite. an analogous fluo-phosphate, although the form of durangite is monoclinic 

 while amblygonite is triclinia 



35. Dyscrasite. T. Petersen (Pogg. Ann., exxxvii. 377), in a review of the analyses of 

 dyscrasite, endeavors to show that there are two native compounds of antimony and silver, 

 to one of which he gives the name sUbiotriargeniite (Ag 3 Sb'-'), and the other, stibiohexargen- 

 . The former has a density of 9 '611-9 '77, and the latter 10-027. All recorded 

 analyses that do not give one of these formulas he considers either to be erroneous or tc>' 

 have been made on a mixture of the above minerals. 



617 A. Eosite. A. Sehrauf, Min. Beobachtungen, ii. 20, in Sitzb. Ak. Wien, February, 

 1871. 



Tetragonal, in minute octahedrons (-J- mm. diam.) a : b : c=l"3758 : 1 : 1. (Basal angle 

 of octahedron 125 : 40'). Inclination of basal plane to octahedral 117° 10'. H. =3—4. Color 

 deep aurora-red, between that of crocoite and realgar, and much darker than red wulfenite. 

 Streak brownish orange-yellow. Heated in the closed tube darkens, but regains its color on 

 cooling. Fused with bi-sulphate of potash gives a mass which is light yellow while hot, 

 becomes, on cooling, first reddish-brown and finally brownish orange-yellow. This dissolved 

 in water and boiled with tin-foil colors the solution faint greenish-blue. Not so rapidly acted 

 upon by muriatic acid as crocoite or wulfenite. When a splinter of eosite is placed on a glass 

 plate, and treated with muriatic acid, with subsequent addition of alcohol, and then gently 

 evaporated, it affords a blue to bluish-green coating, with a green precipitate on the edges. 

 From these reactions, and a series of comparative tests made with crocoite, wulfenite, and 

 vanadinite, Schrauf concludes that eosite is vanadio-molybdate of lead. Found implanted in 

 very minute crystals on pyromorphite and ccrussite at Leadhills, Scotland. . 



122 A. Epiboulawekite. M. Webstyj, ZS. G. Ges., 1869, p. 747. 



Orthorhombic ? occurring in striated prismatic needles G. = 6 "309. Lustre metallic. Color 

 dark bluish gray, almost black. Structure granular, acicular. Analyses, 1.2, Websky (1. c.):. 





S 



Sb 



Pb 



Ni 



Fe 



Zn 



1. Granular. 



21-89 



20-77 



56-11 



0-20 



0-60 



0-29=99-86 



2. Needles. 



21-31 



20 23 



54-88 



0-30 



0-84 



1-32=98-88 



Websky considers the mineral as probably a product of the decomposition of Boulangerite, 

 from which it differs in containing more sulphur and correspondingly less antimony. Found 

 with galena, pyrite, blende, and mispickel, at Altenberg in Silesia. 



132 A. EPIGENITE. T. Petersen, Pogg. Ann, exxxvi; 502, Arsenikkupferwismutherz, 

 Epigenit. 8andberger. 



jrhornbic, observed planes, /, l-£, \-%. Jy\l-*=il0 o 50'. H.=3 - 5. Lustre feebly 

 metallic. Color steel-gray. Streak black. Fracture granular. 



Composition 6Ii S-f-As- S : \ Analysis, Petersen (1. c.) : 





S 



As 



Fe 



Cu 



Bi 



Ag-Zn 



1. 



31-57 



12-09 



13-43 



40-32 



2-12 



tr.=99-53 



2. 



32-:;4 



12-78 



14-20 



40-68^ 



^100-00 





No. 2 is No. 1 after deducting the 2 - 12 Bi which was present as intermingled wittichenite, 

 and as such was combined with 1 '84 Cu and 0'98 S. In the closed tube gives first sulphur 

 then sulphid of arsenic. B.B. on charcoal gives an arsenic reaction and a magnetic slag 

 with - Soluble in nitric acid with separation of sulphur. 



Occ ; iy at Neuglack Mine in Wittichen.. 



