90 
ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE, [bull. 182. 
after they had attained a length of 2 or 3 centimeters there was an 
enrichment of the depositing solutions, as is shown by an undulating 
dark band traversing all the crystals in a general direction at right 
angles to their direction of growth and parallel to the walls of the 
fissure. This dark band, which is usually about a quarter of a centi- 
meter in thickness, is made up of free gold, galena, sphalerite, and a 
minute amount of some unknown telluride, all in very small particles 
embrMld^d in the quartz. After this the quartz crystals continued to 
grow outward for another 2 or 3 
centimeters, containing in this 
portion only scattered specks and 
bunches of ore minerals. The 
direct outward growth of the 
quartz crystals now stopped and 
there was deposited upon the wavy 
surface defined by their pyramidal 
terminations a succession of at 
least 6 distinct coatings, differing 
in color, composed of cryptoc^s- 
talline aggregates of quartz, eal- 
cite, fluorite, sericite, and a little 
chlorite, aggregating in thickness 
about one-fourth centimeter. 
Upon these coatings there was 
next deposited a layer, about one- 
half centimeter thick, consisting 
chiefly of finely divided particles 
of sphalerite, galena, and possibly 
other ore minerals. This is the 
most conspicuous dark band seen 
in the illustration. This baud is 
succeeded by a delicately mottled 
pale-green aggregate of quartz, 
the grains of which sometimes 
contain free gold, calcite, sericite, 
and fluorite, with dark patches of 
ore. This aggregate does not 
exhibit the characteristics of ma- 
terial that has crystallizevl freely in open spaces and is probably, in 
part at least, altered and replaced country rock. Variations from 
the foregoing structure are met witri in various parts of the Camp 
Bird lode, but the specimen described is thoroughly characteristic of 
the richest ore and illustrates well its curious and beautiful banding 
(fig. 9). The conspicuous dark band, locally designated "the worm," 
is the miners' sign for good ore in this mine. 
In the Tom Moore mine the pay streak frequently consists of chal- 
J/'net) 
Fig. 9.— Section through a rich ore band in the 
Camp Bird lode, a, quartz, fluorite, calcite, 
etc.; 6, ore particles including free gold; c, 
quartz. 
