188 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE, [bull. 182. 
very little solid quartz, and the ore occurs in a breccia zone in a latitic 
andesite. The mine was worked in the late seventies and early 
eighties, and was idle in 1899. The workings were then blocked with 
ice and inaccessible. 
From the material on the dump it is evident that the ore, after fill- 
ing the interstices in the brecciated zone of country rock, was itself 
shattered by later movement and cemented by white quartz. The lode 
in the lower workings was apparently not accompanied by much gouge 
and did not possess regular walls. The ore is said to have consisted 
chiefly of ruby silver and argentite in the upper workings. It was 
practically free from lead, although a little galena occurs in the vein 
and some specimens of galena ore were seen from near the southwest 
end of the claim, next to the Mammoth. The ruby silver occurred in 
pockets in the lode. In the lower workings the high-grade silver ore 
is said to have changed abruptty to an ore consisting chiefly of x>yrite 
in quartz, carrying about 12 ounces of silver per ton, with no gold. A 
similar change is said to have been experienced in all the mines on 
Engineer Mountain. 
The country rock immediately alongside of and included in the 
Polar Star lode has been bleached and altered by the ore-bearing solu- 
tions and transformed to a mixture of quartz, kaolin, and pyrite. 
The nature of this alteration is discussed on pages 120-124. 
The ore from the Polar Star was hauled in wagons down to the 
Crooke mill on the Animas, near the mouth of Boulder Gulch, and 
there treated by the Augustine process. It seems to have been well 
adapted to this treatment, a saving ot about 95 per cent being reported. 
Other mines. — The Mammoth, S3^racuse Pride, and Annie Wood 
are all mines on the southern slope of Engineer Mountain upon which 
considerable work has been expended but which are now idle. The 
Mammoth is on a branch of the Polar Star lode, which here shows 
croppings of solid quartz nearly 12 feet in width, dipping southeast 
at 70°. The lode material as seen on the dump is generally similar to 
that of the Polar Star. This mine is reported to have yielded about 
$30,000 in silver and gold. The Mint reports give its total product 
for 1891 and 1892 as $25,655. According to the reports of the Tenth 
Census, stephanite (true brittle silver) occurred in the Annie Wood 
and Mammoth mines, together with freibergite, ruby silver, and sul- 
phide of bismuth. It is quite possible, however, that this is an error, 
due to the very loose use of the term "brittle silver" by the miners. 
The Mammoth and Polar Star are often asserted to be on the San Juan 
Chief lode. As may be seen by reference to the map, where the lodes 
are plotted as accurately as the scale and topography will allow, this 
assertion is improbable. They are probably overlapping fissures. 
The Syracuse Pride shipped ore to Crooke & Co., in Lake City, dur 
ing 1876, and is credited with a product of $10,000 in 1890, but the 
mine was never successful. Some ore was found in the upper work 
