KANSOME.] 
STRUCTURES OF THE LODES. 
67 
si hie mode of deformation and rupture is exemplified," and, it may 
be added, frequently in a single limited field of fracture. The best 
that can be hoped for in any case is to ascertain the dominant mode 
in which fracturing has taken place. 
STRUCTURES OF THE LODES. 
The larger structural features of the various lodes depend* mainly 
upon the character of the fissures in which they were deposited. 
Where the original fracture was a simple, clean dislocation, the result- 
ng lode is. a fissure vein. Most of the lodes of the Silverton quad- 
rangle are of this character— nearly vertical plates of gangue and ore 
•on lined between definite walls. They sometimes show local irregu- 
arities and may divide into numerous branching stringers (stringer 
odes) al their edges, but in the essential character of their workable 
portions they are veins, in the original 
sense of Von Cotta. Such are the veins 
)f the Empire group on Sultan Moun- 
iin, the New York City (fig. 3), Stelz- 
ier. Royal, and Iowa veins of Silver 
Eike Basin, the Green Mountain vein, 
lost of the veins of Galena .Mountain, 
lie Hamlet vein, and many of the lodes 
n the northeast portion of the <|iiad- 
frngle. The width of the workable 
'eins usually varies from a few inches 
ip to lo or \-2 feet. Lodes attaining 
greater width than this are rarely sim- 
ile veins, although some of those near 
fannyside Basin, with widths of from 
to 50 feet, appear to have filled sim- 
ile open fissures. A width of 2 or 3 feet 
iperhaps a rough characteristic average of the productive veins of 
he Silverton region. The vein filling usually fits snugly to the 
ssn re walls and is frequently adherent to them — "frozen," as the 
liners say. Quite commonly, however, there has been sufficient 
lovement along the fissure to cause the ore to come away readily 
rom one or both walls, and sometimes there is a gouge or selvage 
resent. This is rarely thick or extensive. Fissures sometimes con- 
•aei. or pinch, and the vein then becomes much reduced in width 
ml may be entirely absent. Such pinches, where the fairly solid 
alls are separated by a mere crack, were encountered on the New 
1 ~ork City, Stelzner, and other veins, and on the Camp Bird lode. 
j is often difficult, when such a pinch is passed through b}~ a crosscut, 
) believe that it really represents a lode which is elsewhere wide and 
roductive. Many crosscut tunnels have on this account overshot the 
ein sought for. Careful systematic surveying and mapping is the 
feet 
Fig. 3.— Cross section of the New 
York City lode, Silver Lake mine. 
".country rock; b, miners* wall; c, 
broken country rock; d, ore, chiefly 
galena, chalcopyrite, and sphalerite; 
e, ore and country rock; /, ore and 
quartz. 
