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deposit is not enclosed on both sides by the intrusive. It is an alteration and a replacement of limestone by contributions of iron-bearing compounds from the crystallizing intrusive; and fragments of unreplaced limestone may be observed in the tunnel to be completely surrounded by magnetite. The magnetite may also be observed to occur to some extent within shat- tered parts of the quartz diorite, and in some places this rock is altered, as well as the limestone, to a group of typical contact silicates.

An attempt has been made to separate a mass of relatively solid magnetite from an encircling zone of mixed magnetite and highly metam- orphosed rock. The aureole of mixed material contains less than 50 per cent of magnetite by volume. Within this are isolated patches of highly metamorphosed rock, either quartz diorite or limestone. They occur irregularly and presumably are the same as the zones of sheared and altered rock encountered by the tunnel.

The cross-section on line A-B through No. 2 tunnel illustrates the structure of the deposit insofar as it can be deciphered. The section is constructed from the field data obtained from the exposures and from No. 2 tunnel, combined with data taken from Lindeman’s published report on his investigations of 1907. The course of the lower tunnel is not accur- ately known, since its portal is caved; and consequently its location on the map is approximate. The dump from the lower tunnel was examined carefully and was found to consist partly of magnetite, so there is every reason to credit its passing through a zone of that mineral. Regarding the geology of this tunnel Lindeman (16) states that it ‘Shad been run in the same direction (as No. 2 tunnel) for 114 feet into the hill, going through limestone and diorite. The last few feet, however, show magnetite, dipping in towards the hill.”

CHARACTER OF THE MAGNETITE

Much of the magnetite in this deposit is impure, mixed with metam- orphosed rock and impregnated with pyrite. A large part of the outcrop is rusty from the oxidation and hydration of the pyrite. The central part of the deposit, however, as outlined in the figure, contains only small quantities of pyrite and rock. The colour of this part of the exposure is dull black, with an absence of rusty stain, and the magnetite is coarser in grain. Broken, angular pieces of this magnetite show slickensided surfaces, and there is a bluish tone to their black colour.- The detailed character of this body of magnetite may best be illustrated by quoting from the field notes the log of the upper (No. 2) tunnel, distances reading from zero at the portal:

Feet 0— 10: Decomposed rocky magnetite. 10— 14: Sand of garnet with little magnetite. 14— 28: Sheared magnetite with some sulphides. 28— Good grade magnetite with small amount of sulphides. 39— 47: Band of altered silicates. 47— 58: Solid magnetite with considerable disseminated pyrite. 58— 68: Good grade magnetite. 68— 82: Solid lenses of magnetite with considerable sulphides. Some lenses are almost pure magnetite but are short, appearing only in one wall. 82—100: Fairly solid magnetite. 100—108: Sheared and mineralized contact silicates with veins and irregular bunches of magnetite.

There is no information available giving corresponding data for the lower (No. 1) tunnel.