372 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 
to the Whisper ore occurred between levels 6 and 7. Some ore occurs in the dike 
of latite-phonolite on level 2 of the Whisper shaft. Along the west side of the 
phonolite dike on level 6 of the Dante lies another vein which has produced a little 
ore. Ore has also been extracted from the Blue Bird vein on levels 4 and 5. In 
its prolongation this vein would enter the Blue Bird claim a short distance south¬ 
east, but it is not on§ of the main Blue Bird veins. 
BLUE BIRD MINE. 
The Blue Bird Gold Mining and Milling Company owns the Blue Bird claim, 
on the southern slope of Bull Hill. The developments consist of one main vertical 
shaft 1,350 feet deep, with the elevation of collar 10,397 feet, several smaller shafts, 
and about 8,000 feet of drifts and crosscuts. Fifteen levels are turned, the lowest or 
level 151 having an elevation of 9,048 feet. The production is stated to be $300,000. 
The mine was located and worked at an early date. When Penrose visited it in 
1894, it had already attained a depth of 300 feet. 
The country rock on the surface and down to level 4 is latite-phonolite, but at 
about that depth it is replaced by breccia, so that the massive rock seems to form 
a horizontal sheet above the breccia. A phonolite dike about 20 feet wide, with 
the usual platy parting, cuts across the southern part of the claim. Its trend is 
north-nortliwest, and it is probably the same dike which has been noted from the 
Dante and Logan mines. A small northwesterly trending basic dike was observed 
near the southern face of level 4 and not far south of the phonolite dike. Active 
oxidation has penetrated along the veins down to level 4. On the ninth and lower 
levels there is not much oxidation. 
The main vein strikes about N. 5° E. and dips 60° to 90° E. in the upper levels. 
Below level 9 the dip changes to westerly, soon, however, resuming its easterly 
inclination. Locally the vein changes abruptly in strike and dip and is associated 
with much irregular fracturing, dominantly north-south, but of various dips. Some 
east-west fissures occur which do not fault the vein and which carry no one. Two 
shorter, almost vertical veins parallel to the main Blue Bird vein have been devel¬ 
oped in the northern and southern parts of the claim; each is 100 feet distant from 
the main vein, the one to the east, the other to the west. They have been opened 
only to level 4. 
The ores of the Blue Bird have always contained much silver; in places assays 
will give several hundred ounces to the ton. Copper carbonates were found on the 
upper levels. The first appearance of tetrahedrite, which is the principal argentif¬ 
erous mineral, was on level 10. Below the oxidized zone the gold appears in cala- 
verite or sylvanite, which occur chiefly in cracks in the massive fluorite of the vein, 
or in vugs in the same material. Tetrahedrite occurs massive with fluorite or in 
quartz, sometimes intergrown with missive tellurides; it is also found in medial 
vugs in spar veinlets in the deeper levels. It carries both gold and silver and is 
locally accompanied by a little pyrite. Stibnite is mentioned by Penrose from the 
upper levels. Nests of white kaolin,- while common in the upper levels, are not 
known below level 5. The vein material in the main fissure is a compact, fine¬ 
grained mixture of purple fluorite and quartz, which no doubt is formed by the 
filling of open cavities; it contains sharply angular inclusions of little-altered coun- 
