52

most vein about 200 feet west of the Delta surface tram, but its relation to
the vein is obscured by drift cover. Lamprophyre dykes intrude the grano-
diorite on the Delta property and are older than the deposits.

The primary fissuring was followed by alteration of the brecciated
granodiorite along the fissures. Alteration was accompanied by a notable
development of hornblende and actinolite, and the introduction of consider-
able quartz. Following renewed movement along the fissures, the frac-
tured gangue and the hornblende, actinolite, quartz, and altered grano-
diorite were replaced by variable amounts of the ore minerals. The horn-
blende gangue was particularly susceptible to replacement by chalcopyrite,
and the richest ore taken from the mine was of this type. The chalcopyrite-
hornblende ore contains, in addition to the chalcopyrite and hornblende,
variable amounts of magnetite, pyrrhotite, arsenopyrite, pyrite, tetra-
hedrite, safflorite, and molybdenite. The quartz in this type of ore is glassy
and is without banding. There are very subordinate amounts of calcite and
siderite in the ore.

Further movement was followed by the formation of banded, milky
white quartz veins. These veins traverse the chaleopyrite-hornblende ore
or lie along either the hanging- or foot-wall side of the fissure zones. The
banded quartz carries sufficient galena, sphalerite, and tetrahedrite to
make a good grade of silver-lead ore. It also carries pyrite, arsenopyrite,
and chalcopyrite, but only in minute amount. The silver-lead ore is,
however, relatively unimportant, as the banded quartz veins seldom exceed
half a foot in width or 100 feet in length.

The completed development work consists of more than 2 miles of
crosscuts and drifts, 2,200 feet of raises, and 330 feet of winzes.

No. 1, the lowest or main crosscut adit at elevation 4,100 feet, is
driven for about 3,100 feet northwest into the mountain and intersects
four fissures with drifts on each. It is connected to the drift on the lowest
fissure by two raises and stopes. The entrance to this adit has been sealed
by a boulder slide that was brought down by a rush of water from No. 4
adit and these workings are not accessible.

No. 2 adit, at elevation 4,365 feet, extends northwest as a crosscut
for 180 feet to the lowest fissure zone. From there the fissure is followed
by a drift for 1,400 feet on an average bearing of roughly south 75 degrees
west. The drift extends 1,340 feet west and 60 feet east from the crosscut.
There are a number of raises and stopes in what were the richest parts of
the fissure, but judging by the exposures in the roof of the drift, a consider-
able tonnage of low-grade ore remains.

An 18-inch channel sample was taken across the deposit in the roof of
the drift 280 feet west from the main crosscut. Here the zone consists
largely of brecciated granodiorite partly replaced by hornblende and chal-
copyrite, but on the foot-wall side there is a 2-inch seam of milky white
quartz carrying galena, sphalerite, and tetrahedrite. The 18-inch sample
assayed: gold, 0-04 ounce a ton; silver 16-33 ounces a ton; copper, 3-35
per cent; lead, 8-24 per cent; zinc, 11-44 per cent. About 400 feet west
of the crosscut a 28-inch channel sample taken across the zone in the roof
of the adit assayed: gold, 0-095 ounce a ton; silver, 1-55 ounces a ton;
copper, 5-53 per cent. This sample was of brecciated granodiorite only
sparsely mineralized with chalcopyrite and is representative of a very