Rocky Mountain Tunnel EarthCache
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Surprisingly, the knowledge of a tunnel running beneath the
township of Beechworth in the north east of Victoria is not
particularly well known. The tunnel is not signposted, but it is
mentioned in the local tourist brochure and access to the mine
entrance is possible, albeit with difficult terrain. The slope is
steep, the ground is loose and uneven and there are quite a few
bushes near the entrance.
HISTORY
Beechworth was a major gold mining centre during the end of the
19th century with a number of mines operating in the region. When
traditional mining techniques had exhausted the supply of surface
gold, more advanced methods of gold mining were required.
The site of Lake Sambell was in fact once an open cut mine and
reportedly still contains a commercial quantity of gold in its
base. The gold was removed from this mine using a method known as
‘hydraulic sluicing’, a process by which water under
high pressure is used to break down large amounts of rock and earth
to expose the gold within them. Unfortunately this process left a
great deal of water and sludge at the base of the mine, so a
decision was made to build a tunnel underneath the township from
the lake to the nearby gorge in order to drain this waste
away.
The tunnel began construction in1876 and was completed in 1879 at a
cost of £13,000. The construction of the tunnel itself also
removed another 180 kilograms of gold, not a bad haul when compared
to the 80 - 140 kilograms removed from other mines in the
area.
GEOLOGY
The township of Beechworth is built at a junction of various
granite types and colluvial sedimentary rocks, ranging in age from
the Devonian Period right through to the Tertiary Period (a few
hundred million years in difference.). The granite through which
the Rocky Mountain Tunnel was cut is high in silicon dioxide (SiO2)
and mostly I-type (Douglas & Ferguson, 1988). The tunnel was
dug by men with basic tools and limited use of explosives to aid
them. This was no mean feat, unweathered granite is a very hard
rock and would have been difficult to mine.
To log this Earthcache you are required to email your answers to
the following questions to me.
1. Examine the grain size of the granite at the cave’s
entrance and explain what that indicates about the granite’s
rate of cooling.
2. Why were explosives used sparingly to remove granite from
the tunnel?
3. Visit the historical sign at S 36° 21.515 E
146° 41.704 and tell me the amount of gold yielded from
Lake Sambell.
4. Post a photograph of yourself at the tunnel entrance as
evidence of your visit. Photographs must have people in the photo.
A hand holding a GPS receiver is acceptable.
I encourage you to comment on what you enjoyed or found interesting
at the location when logging your visit.
Logs that do not meet these requirements
will be deleted at the owner’s discretion.
References
Douglas, J.G., and Ferguson, J.A. (Eds.), 1988, Geology of
Victoria, Victn. Div. geol. Soc. Aust., pp. 1 – 665
Thanks to Rhinogeo for the use of this resource.
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