258 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE, [bull.182. 
westward to intersect the lode from a point about 150 feet above the 
qottom of the gulch. All the workings are in andesitic rocks, chiefly 
breccias, of the Silverton series. The ore occurs in a brecciated zone 
which is usually from 3 to 5 feet wide. The hanging and foot walls 
are well defined by planes of recent slipping, that on the hanging 
wall being especially regular and continuous. These slip planes usu- 
ally contain a little soft gouge. Between these walls the ore occurs 
in stringers and bunches, partly replacing the shattered country rock 
included within the breccia zone. It consists of pyrite and chalcopj'- 
rite and occasionally a little galena. Pyrite is yery abundant, occur 
ring in solid masses, which, however, are not mined unless they contain 
chalcopyrite. Next the hanging wall there is a persistent seam, some- 
times a foot in width, which consists of crushed country rock with 
sometimes a little white quartz. This portion of the lode is worthless, 
although a little sphalerite and tetrahedrite are said to occur in the 
quartz. No quartz was seen with the pay ore. The lode is not every- 
where productive. There are frequent barren intervals, where the 
space between the walls is filled with broken and altered country rock 
impregnated with pyrite. The wall rock is impregnated with pyrite 
for at least 150 feet from the lode, but no ore is mined outside of the 
walls of the fissure. 
The ore is low grade as a whole, containing from 0. 05 to 0. 1 ounce 
of gold and 12 to 30 ounces of silver per ton, with up to 30 per cent 
of copper. In 1900 the mine was reopened after some years of idle- 
ness, and it was proposed to treat the ore in a new smelter then near- 
ing completion at the point where Cement Creek enters Bakers Park. 
The lowest tunnel, which in September, 1900, had a length of about 
550 feet and had not yet cut the lode, exhibits well the rather remark- 
able mineralization of the Silverton breccias in this vicinity. AIL the 
rock passed through is heavily impregnated with fine pyrite and fre- 
quently contains small sporadic bunches and stringers of galena and 
sphalerite. In some places the andesitic breccia has been locally 
silicified. 
The Henrietta lode is of theoretic interest from the fact that the 
ore, in its freedom from quartz, presence of kaolin, and partial replace- 
ment of country rock, as well as in mineralogical character, is similar 
to the ores occurring in the stock deposits of Red Mountain. At the 
Henrietta, however, it is found, not in stock, but in a distinct fissure. 
Other mines and prospects. — From Prospect Gulch southward to 
Silverton are many prospects along Cement Creek and in the side 
gulches. None of them are yet of much importance and not all were 
visited. The most ambitious of these is the Yukon tunnel of the 
Boston and Silverton Mining Company. No ore has yet been pro- 
duced, but the tunnel is supplied with a new mill equipped with 
Blake crusher, rolls, jigs, 10 stamps, 2 Wilfley tables, and 4 Frue 
vanners. The power is steam. 
