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The greater the twist to a field the greater the tendency for the fractures to gc out like fins from the troughs.
The
rich occurrence worked out by the Birthday Company appears to have been
a centre for the reception of unobstructed drainage from a long extent
of gold-slate, to the north and upwards. Its originally narrow form has
been much enlarged as a consequence of the draining fluids, containing
material that would deposit sulphides and quartz, having become
incorporated with the wall matter. The wavy unevenness of its
foot-wall furnished numerous minor points of catchment for gold. The
general obstruction to the gravity " pull" on the drainage, caused by
the walls coming together, terminating the ore occurrence, had the
greatest influence in making that spot a store of gold. The area of the
Birthdav mine happened to have all of this position within its bounds.
It extends for about 800 feet south from the shaft, and the " bow " end
of the position was met with near the boundary. It was the top part of
this " make" of quartz that the Le Page-party met with near the
surface. It proved to be very rich. (See Fig 7.) The Birthday Company
has mined from it up to date about 60,000 oz. of gold, from the
proceeds of which it has distributed in dividends more than.. £115,000. Less than £2.500
of capital was used in bringing the mine to its: dividend stage. The
shaft is down 800 feet, and works are opened into great widths of
tadpole-shaped formations of quartz of low grade. No doubt lower works
will meet with large bodies of similar low-grade ore. The-pitch of
these masses continues south at the same angle as noted higher 'about
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30 deg. from the horizontal), and, as a consequence, all works have to be taken farther south, as depth is reached, before the line of stone is entered, .as usual in this class of lode, the deposition of gold is in patchy form throughout,;: the:
bulk of the formation. There appears to have been a slow enlargement of
lode in' progress on either side of the original channel of drainage.
As this enlargement went on, other lines of gold drains were
intercepted. As these became incorporated in ihe lode
formation, their original lines were marked by bluish-coloured lines of
almost vertical quartz, slightly laminated. Down such lines gold has
been deposited in fine and coarse grains, associated with sulphides of
iron (pyrites), and a little sulphide of lead (galena). The long
occurrenc of rich deposit above these thick " makes " intercepted the
gold that would otherwise have found storage in them. The whole of this
thickened feature of fracture pitches south into the area of the South
Birthday Company. This company went to work soon after the Birthday
Company commenced operations. It tried to locate the Birthday run of
rich stone as it continued south. The channel was soon found, having
little or no quartz, and all works down to the 500-feet level failed to discover
anything of value. The Birthday's rich gold occurrence reached only as
far as the boundary dividing the two areas. Beyond this its channel was
in " track " form. A medley of breaks in the rocks (known as
cross-courses and slides) also caused much trouble to the management. A
survey down to the 500-feet level would have done this company much
service. Not far below this level the "ridge" of the thickened part of
the fracture was met with. Works opened at 800 feet from the surface,
went right into its " makes." They are of the same class as met with in
the Birthday, and belong to the same system of thickened fracture. The
South Birthday Company met with these formations on their "ridge," and
the Birthday went into their "keel." The ore is all
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