MINES OF BULL HILL. 
373 
try rock. This material is sometimes 3 feet in width. Secondary fracturing with 
opal and drusy quartz is often noted, and the ore seems to be associated with these 
disturbances. In places, such as in level 10, the vein appears as a sheeted zone 6 
feet wide, divided in slabs about a foot thick. On level 4 the fissures pass through 
the phonolite dike, but no values are contained in the dike. On the twelfth and 
lower levels the vein shows fine parallel sheeting, with a great number of veinlets of 
dolomite which carry fluorite and tetrahedrite. The slight developments on level 
15 show again the large fluorite vein with sharply defined inclusions of breccia. It 
is seen here that the spar veinlets are younger than the compact fluorite. 
The main vein is opened for 900 feet horizontally, but the deep developments 
are confined to the vicinity of the shaft and a few hundred feet south of it. The 
surface shoots on the main vein extended down to level 6, 400 feet deep. One part 
seems to dip about 45° N.; the maximum length along the levels was 400 or 500 feet. 
A smaller, northerly shoot almost connecting with this seems to dip southward, 
but extended only to level 3. From level 11 down to the bottom ore is stated to 
occur again. Some very fine specimens of tellurides and tetrahedrite have been 
found in this part of the mine. 
DEXTER MINE. 
The Dexter mine, situated on the Dexter claim, lies to the south of the Blue 
Bird, on the southwestern slope of Bull Hill. It is owned by the Dexter Gold Mining 
Company and is being worked under lease. Sinking was in progress at the time 
the mine was visited, the shaft being then 560 feet deep. Four levels have already 
been turned and a station cut for the fifth. The elevation of the collar is about 
10,300 feet. Three other shafts on the property, now abandoned, increase the total 
developments to about 3,000 feet. The production of the mine has not been very 
large. 
The shaft starts in the pitted, oxidized latite-phonolite which is characteristic 
of this slope of Bull Hill. As in the near-by mines, this rock is found to overlie brec¬ 
cia as a flat sheet. Level 1 is closed. Level 2, 200 feet below the surface, is in 
breccia, but the top of a 40-foot stope above this level shows the approximate con¬ 
tact of the two rocks. Three hundred feet S. 15° W. of the shaft on level 2 the con¬ 
tact is again seen, breccia to the east and latite-phonolite to the west. The contact 
is by no means sharp and its dip and strike could not be determined. A dike of 
latite-phonolite 20 feet wide crosses the level about 145 feet south of the shaft. The 
remaining workings of the mine are in breccia. 
The veins of this mine belong to one very well-defined system, apparently 
corresponding to the westernmost of the three Blue Bird veins, a short distance to 
the north. They trend slightly east of north and dip very steeply to the west. 
One of these veins just west of the shaft, called the Fluorite vein, is a sheeted, 
partially oxidized zone in breccia, with kaolin and a brownish-black manganese 
oxide in the seams and a 2- to 8-inch seam of dark-purple fluorite sometimes carrying 
quartz. Fifteen feet farther west is a nearly parallel vein carrying more manganese 
and no fluorite, but otherwise similar. This is known as the Manganese vein. 
About 100 feet south of the shaft, on the 280-foot level, these two veins come 
together and continue for 50 to 60 feet, when they finally cross and resume their 
former courses. A 50-foot crosscut, east from the shaft on the same level, reaches 
