ujsomb.] THE STOCKS OR MASSES. 109 
CHARACTER AND STRUCTURE OF THE ORE. 
It is very difficult, on account of the present condition of the mines, 
> give a satisfactory account of the mineralogy and structure of the 
*es occurring in the stocks. The chief difference between these ores 
id those occurring in the lodes seems to have been the fact that the 
firmer occurred in nearly solid masses, with very little gangue. The 
xmrrence of enargite, moreover, is apparently peculiar to the stock 
eposits in this region, the mineral not being known in the lodes. It 
Des not, however, occur in all of the stocks. The more common ore 
inerals of the latter are galena, sphalerite, tetrahedrite, enargite, 
ialcocite (stromeyerite), bornite, chalcopyrite, and pyrite. While 
ie galena ore of the upper levels was argentiferous, the highest 
lver values occurred in connect ion with the copper-bearing minerals, 
specially the chalcocite, bornite, and chalcopyrite. These three ore 
inerals were almost invariably accompanied by pyrite. In the 
cher portions of the ore bodies the pyrite was subordinate, and 
jpears to have been found chiefly in the peripheral portions of the 
ocks. But in the poorer ores the argentiferous copper minerals 
ecurred as nodular bunches in masses of low-grade iron pyrite car- 
ing 1 1 1 > to 5 per cent of copper and a little silver, usually less than 
Jounces per ton, and a fraction of an ounce of gold. The pyrite 
mally forms a rather line-grained and sometimes crumbling aggre- 
ite, but ui the Zuni mine occurs in beautifully sharp octahedra 
nbedded in white kaolin. Bismuthiferous ores of silver and lead 
jcurred in some of the ore bodies, notably in the Silver Bell and 
enesee-Vanderbilt. Specimens from the latter mine contain a 
tight lead-gray mineral having the physical properties of cosalite, 
fetich chemical tests show to be slightly argentiferous sulphobis- 
uthite of lead containing a Little copper. Cosalite occurred also in 
*e Yankee Girl. The rare mineral, kobellite, a sulphantimonite of 
ad witli bismuth partly replacing the antimony, was found in the 
lver Bell mine, 1 carrying from .'5 to 4 per cent of silver. The 
lly other known occurrence of this mineral is at Hvena, Sweden, 
he rich silver ores proustite and polybasite occurred in the Yankee 
irl, Genesee- Vanderbilt, and probably other mines of this district, 
ennantite is reported to have occurred in the National Belle mine, 
inkenite has been described by Hillebrand 2 from the Brobdignag 
aim, a now abandoned prospect in the Red Mountain Range near 
iattanooga. Guitermanite and zunyite occur in the Zuni ore body 
id in a few prospects close to the latter, the zunyite as small spark- 
tig, colorless tetrahedrons embedded in the massive, bluish lead- 
'ay guitermanite. Barite is apparently always present in the ores 
! the stock deposits. It often occurred as isolated crystals or crys- 
lline masses embedded in the argentiferous bornite of the Guston 
1 H. F. Keller: Zeitschrift fur Krystallographie, Vol. XVII, 1890, pp. 67-72. 
2 Proc. Colo. Sci. Soc, Vol. I, 1883-84, p. 127. 
