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COIMPMIB IC SIE AG ise WAIN SS (OVE AT EIEISNCA ID SIMRO I 575

quartz and other gangue. In some of the specimens there were
some malachite and much limonite, indicating oxidation. Co-
vellite is extensively developed along cracks in the bornite but
is seldom seen in the chalcopyrite. The cracks in many cases
proceed through the chalcopyrite but the solutions have pro-
duced no visible effect. This is an excellent example of selective
replacement. Chalcocite is almost entirely absent from the King
vein, and was seen in only one specimen, where it occurred along
minute cracks in almost microscopically small amounts.
Maegnetite ore begins to appear about 100 feet south of the
main shaft, and the magnetite gradually increases in amount until,
at the highest part of the ridge, the vein is almost solid magnetite,
with a small amount of quartz. The magnetite is well crystal-
lized when it occurs as small grains in the quartz, but the larger
areas are irregular in outline and appear to replace the quartz.
The smaller crystals are much more homogeneous than the large
areas but contain small specks of chalcopyrite, bornite, and small
veinlets of hematite, which are either confined to the crystal in
which they occur, or to a narrow space along the margin. The
larger areas of magnetite contain a great deal of hematite which
appears to be of two generations. The larger amount is in the
characteristic form of bundles or sheaves of narrow blades, often
with a radiating habit. These blades are, however, extensively
corroded, so that in the majority of cases there is nothing but a
ragged skeleton left, with just enough hematite to suggest the
original form. Besdies this, there is a considerable amount of
hematite which occupies small veins cutting the magnetite, or sur-
rounding it in the gangue contacts similar to the hematite in the
small magnetite crystals. This is clearly later than the magnetite,
and the hematite blades are just as clearly of an earlier date. All
the magnetite is impregnated with chalcopyrite, bornite, tetra-
hedrite and probably some native silver, forming a structure which
is remarkable if not unique. The sulphides are also disseminated
in the gangue, but as larger grains. In both the gangue and the
magnetite the copper minerals are slightly altered to covellite
and secondary chalcopyrite and are replaced by limonite. Cer-
tain pseudomorphs of covellite, after bornite or chalcopyrite,