4 Tunnels 4 Gold (Dunedin, Otago) Traditional Cache
Hidden : 11/17/2013
Difficulty:
2 out of 5
Terrain:
3 out of 5

Size: Size: regular (regular)

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Geocache Description:

A short but very steep walk down the Tunnels track to four forlorn goldmining adits.

This is a Department of Conservation track through pine forest. Placed with kind permission from City Forests.

# As the sign advises, the tunnels are not safe – DO NOT ENTER.
# All historical sites are legally protected.

There never was much gold here (and what there was has gone) but hopeful miners in the 1860’s and again in the 1930’s put a lot of effort into searching for it. You'll be prospecting for a 1.6 litre screwtop nugget - but the only hard labour needed is the 180 m climb back up the hill afterwards!

See below for how to arrange a key to the gates on Mountain Road. While you're in the area, why not make a day of it and continue to Yellow Ridge Commemorative (1 1/2 hours walk) and The Ultimate Gap (2 1/2 hours walk)?

From the Mountain road carpark, descend the Tunnels track about 10 minutes to the signposted track junction. The main track on the left continues down, crosses the Waikouaiti and on up to Cox Hut and Yellow Ridge. Take the right-hand track; 5 minutes further downhill you will cross a waterrace where a signpost points right to the Tunnels.

After finding the cache, you can continue from the Tunnels sign on a marked track along the water race to rejoin the main Silverpeaks track to Yellow Ridge. Or, explore along the Waikouaiti riverbank to find more water races and hummocky mined-over river flats.

There’s gold in them rivers…

The gold was here because the Silverpeaks are formed from Haast schist, the basement rock of Otago. See the schist in shades of purple on the GNS NZ Geology webmap. (Select background layer Topo 250 and toggle ”Geological Units” on/off to identify the area; click on the map to see the geological information for that point.)

This schist began forming 250-130 million years ago from sand and silt deposited off the Australian coast of Gondwanaland. By 180-160 million years ago these sedimentary rocks were buried 15 km deep and metamorphosed into schist. Under heat and pressure new minerals formed, such as mica which crystallises out in flat parallel sheets. It is the rocks breaking along these parallel mica sheets which causes the characteristic schist slabs.


Gold

From around 150 million years ago, Otago’s 1860’s goldrush was deposited in the thin veins of white quartz in the schist. Superheated water (200–400° C) dissolved minerals from even deeper rocks. As this mineral solution rose towards the surface through fractures in the schist the temperature dropped. Between 12 - 3 km deep, gold, scheelite (tungsten ore), iron pyrites (fools gold) and other minerals crystallised out along with the quartz. This process is still going on today- there is still gold being deposited underneath the Southern Alps.

As the schist mountains are uplifted, they get worn down – over the past 2 million years, about 20 vertical kilometres of rock have weathered away and washed downriver out to sea. Since gold is 19 times denser than water, the gold eroded out of the quartz veins wasn't carried far. Instead, the gold fell to the riverbed and became concentrated in river gravels. It is this alluvial gold that the Waikouaiti miners were looking for.

Mining

There was a goldrush into the Waikouaiti River South Branch in May 1864, attracting about 150 people. Otago Witness 4 June 1864. However, the hopeful miners got “only a few specks to the dish”. “There were no provisions on the ground, and from the excessive steepness of the spurs, packing on horseback is impossible” Otago Daily Times 4 June 1864. The rush turned out “most unsatisfactory” Otago Witness 11 June 1864.

See how busy the miners were from the Archaeological Site Recording Map; each star on the South Waikouaiti River is a mining site (NB: all archaeological sites are legally protected).

In the depression of the 1930s there were half a dozen groups of miners trying their luck in the Waikouaiti River. There was a government goldmining subsidy of 30 shillings a week for married men or 15 for single men, which ceased once they had found the equivalent value in gold.

The Key

Unless you're a mountain biker, it's easier with a key to the Mountain Road gates!
Here’s how to save a 5 km/ 1 hour walk each way: apply online for a permit at City Forests website.
The Forest Asset Coordinator, Ross Chambers, has done some geocaching himself...

Permits are processed only once a week, usually on Mondays, so you need to plan ahead. You need to say where, why and dates you want access, car type and registration, address, phone, date of birth, shoe size, cat’s favourite food... Then go to the office at 31 Stafford St to sign the permit - there's a $500 bond - read a list of conditions (carry fire extinguisher and shovel, have dipped headlights on, no smoking, maximum speed 50 km/h etc) - and pick up the key.

Additional Hints (Decrypt)

[Explicit, since only 13 m accuracy] nybat jngre enpr cnfg 5gu ghaary

Decryption Key

A|B|C|D|E|F|G|H|I|J|K|L|M
-------------------------
N|O|P|Q|R|S|T|U|V|W|X|Y|Z

(letter above equals below, and vice versa)


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