F, A. Genth—Contributions to Mineralogy. 321 
which I have made, gave, after deducting 4-22 p. c. of quartz, 
the following result: 
Copper, 38°16 requires § for Cu,S 9°63 
Silver, 3°21 i er 0°48 | 1 3.791-9) 
Zine, Ont oe a ens 3°07 os 
Tron, 1°05 # “«  .FeS 0°60 | 
Arsenic, trace 
Antimony, 24°67 Se 1 ae 9°84 =? | 
. Sulphur, 26°97 ps oo 
100°29 23°62 
_. The material for analysis appeared to be free from other 
impurities than quartz, and it is difficult to account for the 
large excess (3°35 p.c.) of sulphur. The other constituents 
agree very well with the tetrahedrite formula b 
Want of material prevented a reéxamination. 
7. Brochantite from Arizona—This mineral occurs in mi- 
Bill Williams’ Fork, Arizona. I analyzed a foliated piece, 
which, however, was somewhat mixed with chrysocolla and 
cuprite, and found: 
i IL. 
Water 14°46 ee 
Chlorine 0°31 0°33 
Ferric oxyd 0°33 0°52 
Cupric “ 67°75 67°69 
Sulphuric acid 13°55 13°27 
Silicic ee = ee 3°59 
100°00 
This would give: 
Brochantite, Cu0O,SO,+3CuOHO 76:49p.c 
i CuCl+ Aly gga 2°10 
1 * 
Chrysovclla, (?) Cu0,810 44 2°68 
socolla, (?) CuO,Si 6 
Tinonite, Ve ’0,+-3HO 0°38 
Cuprite, Cu,0 "96 
Water, 0-47 
100-08 
This is of course to be considered only as an approximation 
to the composition of this mixture. A more correct caleula- 
tion could only be made after the composition of the ataca- 
mite and chrysocolla from Bill Williams’ Fork had been es- 
tablished, 
Philadelphia, March 1st, 1868. 
Am, Jour. 8c1.—Seconp Ssrigs, Vou. XLV, No. 185.—Mar, 1868. 
21 
