YORK TIN REGION. 
53 
forms in bristling feathery crystals over every object in the mine. Near the entrance the 
surface water dripping from the roof forms icy stalactites and stalagmites that later grow 
together, making gradually thickening pillars, which, unless removed, choke the tunnel. 
A short distance from the mouth of the tunnel a large limestone inclusion was passed, 
through which formed the upper 4 feet of the tunnel for a distance of about 28 feet. Fault- 
ing was evident along the edges of the limestone. About 100 feet from the mouth of the 
tunnel another inclusion of limestone was struck that was in a broad band 10 to 20 feet 
thick, striking about northwest and dipping variably northeast. Along both sides of this 
limestone was a considerable amount of iron oxide, carrying some tin. The contact of the 
limestone and granite was followed to the northeast about 52 feet, where the dip became 
almost vertical. A winze was sunk 20 feet, when the dip became gentler (17°), but 70 feet 
from the winze the contact dips 37°. 
From the foot of the winze an incline with its floor on the limestone has been run about 
90 feet, parallel to but in the opposite direction from the main tunnel. Tin-bearing veins 
Scale 
i 
LEGEND 
2 feet 
W&: 
>r; 
Granite, Quartz with Tourmaline Quartz with 
country rock kaolinized cassiterite 
mineral and tourmaline 
Fig. 10.— Diagrammatic; section of cassiterite-bcaring replacement vein in North Star mint 
were struck at several places along the course of the incline and drifts turned off at two 
places. One of these 60 feet from the winze is 18 feet long, turning to the north and then 
to the east, and is said to carry pay ore, but had not been systematically sampled. The 
second drift, 70 feet from the winze, turned southward under the main tunnel. At the 
point of turning 3 feet of rock much impregnated with iron oxide and carrying a large 
amount of cassiterite were encountered. When thawed, the rock fell to pieces, being finely 
crushed through the whole width. This particular place seems to be the junction of a num- 
ber of faults which carry but little gouge and whose character and extent are unknown. 
Near the faults the granite is sometimes much changed, having lost most of its feldspar, 
which is replaced by quartz, black tourmaline in very fine crystals, and varying amounts 
of cassiterite. It seems likely, also, that the quartz has been largely replaced by secondary 
quartz, as it shows none of the "smoky" appearance so common in the area, and that 
