ARCHAEOLOGICAL FEATURES RELATED TO COPPER MINING (1842-1867) AT MINERS HEAD, GREAT BARRIER ISLAND

by P.R. Moore State Highway 25, RD 1, Waihi

SUMMARY

Copper mining at Miners Head, Great Barrier Island, spanned a period of at least 25 years from 1842 to 1867, or possibly later. Only about 2500 tonnes of copper ore was produced.

Archaeological features relating to the mining of copper include the mine itself, other exploratory workings, the stone foundations of a building, and a 1 kilometre long water race. The majority of these features have not previously been recorded.

INTRODUCTION

The geology and workings of the copper mine at Miners Head - in its latter years known as the "Otea Mine" - have been described by Hutton (1869), Bartrum (1921), Henderson (1931), and Gregg et al. (1970). However, other features relating to the mining, including a building and water race, have not previously been recorded.

A brief survey of historic archaeological sites in the Miners Head area (Fig. 1) was carried out during the Offshore Islands Research Group trip to Mine Bay from 30 December 1988 - 7 January 1989. This survey was by no means comprehensive and, because of bad weather, few of the sites could be examined in detail. Hence there remains considerable scope for further work.

MINING HISTORY

Although the existence of copper mineralisation at Miners Head was known as early as 1837 (Williams 1965), there seems to have been no attempt to exploit the rich lode until 1842, when four Cornish miners were involved in "trial sinking and driving" ('Auckland Chronicle' 31 December 1842, Moor 1987). They produced nearly a tonne of ore, containing 40-60 % copper. By April 1843 about 20 men were employed at the mine, and a parcel of 100 tonnes of ore was later shipped to Sydney ('Southern Cross' 22 April 1842, Moor 1987; Henderson 1931).

Up to May 1857 a total of 730 tonnes of copper ore, of unknown grade, had been taken out of the mine, and between 1857 and 1867 a further 1500 tonnes was produced (Hutton 1869), containing perhaps 15% copper (Henderson 1931).

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This was the most active period in the mine's history, and from what Hutton was able to ascertain during his visit in December 1867 the work was carried out by several different parties and companies. These included: the Abercrombies and Messrs Whitaker and Heale (up to May 1857), Messrs Ninnis and Rowe (1857-1858), the Great Barrier Co (1858-1861), and finally the Otea Copper Mining Co (1861-1868?). There seems to be no record of operations after December 1867, and mining may have ceased during 1868.

Fig. 1. Map of the Miners Head area, northern Great Barrier Island, showing the location of historical archaeological features.

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T H E C O P P E R M I N E

The main workings are located on a promontory about 600m northwest of Mine Bay known as Miners Head (Fig. 1). Lower levels of the mine comprise a large, partially collapsed, chamber measuring roughly 45m long, 15-18m wide, and more than 30m high, with a vertical shaft, reputed to be 22m deep, at its narrow southern end (Fig. 2). The shaft is completely flooded. About 12-15m directly above the shaft is a 2m wide adit, blocked by timbers, and a second adit 15-20m above that. At the northern end of the chamber the roof has collapsed, providing access to the surface.

The main part of the lode, which was originally 7-12m wide, has been almost entirely worked out, except at the southern end of the chamber where it thins to only 2-3m. At the bottom of the shaft it is also reported to be about 3m wide (Hutton 1869). The lode consisted of shattered rock containing nests and nests and pockets of chalcopyrite and pyrite with minor amounts of copper sulphates and oxides (Gregg et al. 1970). Walls of the chamber are heavily copper stained, particularly on the western side, where drilling marks are still evident in places.

Access to the chamber is via a 50m long drive from the SE corner of the headland (Fig. 2). It is 1.3-1.5m wide and 1.5-1.8m high. There are some old timbers at the portal, and in a few other places, but in general the roof is unsupported. The portal is only about 2m above the high tide level.

The upper part of the mine con-sists of a network of short, probably interconnected, adits, at least 6 of which are visible near the top of the near-vertical northern cliff face. These are virtually inaccessible without the use of a rope or ladder, and originally must have been reached either by a catwalk, or by rope ladders lowered from above. Alternatively, access to Fig. 2. Plan of the main chamber (or stope) these workings may have been gained via the adits above the shaft, in the

of the copper mine at Miners Head (after Gregg et al. 1970).

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main chamber. To my knowledge these adits have not been examined by geologists.

East of the upper workings the crest of the headland has been levelled off, and ore extracted from the adits was probably passed down from there, via a wooden shute, to a bench level cut into the cliff face (on the southern side) about 20m a.s.l., and thence down to the beach just east of the main access tunnel. A channel cut into the cliff face, marking the position of the shute, is still clearly visible (Fig. 3).

There are also 3 small adits (or rather one, branching, adit) approximately 100m west of the main drive, and only about l m above high tide level. The main adit is about 10m long and trends NNW; minor copper staining is present on the walls. The eastern branch is 4m long, and has a 2m x l m x l m deep shaft within it. Other adits on the northern side of the headland, situated just above sea level, were not examined.

O T H E R F E A T U R E S

There are a number of other features associated with the copper mine located in the small bay on the southeastern side of Miners Head. The most significant of these comprises the remains of an old building, situated just above high tide level and about 20m SE of the main access tunnel. Only the stone foundations and chimney base are still preserved (Figs. 3,4,5).

This building originally measured about 9m x 7m, and was presumably built mainly of timber or iron, which have since been removed. The foundations were constructed from unshaped, partly shaped, and a few well-trimmed blocks of local stone cemented together with coarse grit and lime. In the N W corner the foundation blocks were placed upon 2 large timbers; the reason for this is unclear. There are also some large timbers on the northern side of the building (largely buried beneath rubble) which appear to have formed part of a small annex, possibly used for sorting and washing the copper ore. Such a function is suggested by (a) proximity to the ore shoot from the upper workings and (b) the presence of a wooden flume, only about l m of which is exposed (Fig. 5). Water may have been diverted into this flume from a shallow concrete channel or culvert which extended about 20m around the cliff face to the southeast, to a small stream.

The building appears to have been of an open plan design, and may have been used as a changing room, store room, and workshop. Hutton (1869) makes no mention of any buildings, but it was most likely constructed during the main mining period, between 1857 and 1867.

Approximately 30-40m south of the old building the rock outcrop has been levelled over an area of roughly 7m x 5m. A small heap of rusty bolts and

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Fig. 3. Archaeological features at the SE end of Miners Head (from left to right): portal of

Fig. 4. Closer view of the old building foundations, from the south. Note the 3-tiered construction of the outer wall (foreground), and stonework of the chimney base (centre).

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lengths of iron plate on this area suggests it could have been occupied by a winch or other heavy machinery. Just to the north there are several deep slots cut into the rock (for large timbers), and also numerous iron bolts still in place. This was possibly a loading area for bringing heavy machinery ashore, or perhaps the site of another building.

No evidence of a tramway linking either of the above sites with the building, or mine, was found. Ore from the mine was probably shipped out from a small wharf situated about 50m west of the access tunnel.

approx. high tide level-*i

SEA

chimney 'cavity

brick-lined chimney-)

1.5m high wall - A \ (3 levels of stonework)\\

path to streom^\ (with culvert)

cavity fireplace c. 1m

Fig. 5. Plan of the old building (foundations only) at Miners Head, and detail of the chimney base (viewed from the south).

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MINE BAY

Apart from the main copper mine, there are also several prospecting adits in the area. The largest of these is situated in a narrow cleft in the coastal cliff on the north side of Mine Bay, about 2m above sea level (Figs. 1,6). The adit is about 20m long, generally l m wide, and an average of 1.5m high. A shallow, 2.5m x lm, pit at the entrance to the adit may represent an infilled shaft.

The adit, which follows a thin breccia dike and fault zone containing minor copper mineralisation, was recorded by Bartrum (1921) in 1919, but was not mentioned by Hutton (1869). Hence it may have been excavated after 1868.

The miner's camp was presumably situated on the relatively large area of flat land at the head of Mine Bay. Unfortunately this was covered in long grass at the time of our visit, and no definite archaeological features were recorded. Any structures (e.g. stonework) have probably also been Fig. 6. Plan of the prospecting adit on the considerably modified by campers and n o r t h s i d e o f Mine Bay ( s e e F i 8 - 1

. . . . . for location), casual visitors over the years. The camp was linked to the mine by a well-formed track (Fig. 1), although the northern part has largely been obliterated by erosion.

VILLAGE CREEK

There are a number of historic archaeological features inland from Mine Bay, the most significant of which is a water race extending for over 1km around the northern side of the valley, and generally 10-15m above stream level (Fig. 1). The race is still well preserved in places, and averages about 1.5m wide and 0.5m deep. However, just south of the second northern tributary the race crossed a prominent rock face, and at this point water must have been

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channelled through a metal pipe or wooden flume. Two iron stakes, which pre-sumably formed part of the support structure, are still situated in the rock face.

Near its upper end the race passes through an S-shaped tunnel about 15m long, 1-1.5m wide and, originally, probably more than l m high (Fig. 7a). The tunnel has been excavated through a narrow spur. East of the tunnel the race is in particularly good condition, and is up to 2.5m wide and 1.3m deep.

At the head of the race are the remains of a low wooden dam across the main stream, at an elevation of approximately 20m a.s.l. (Fig. 1). The dam is 13.5m long and 0.5m high, and constructed from at least two roughly shaped timbers secured with large iron bolts. The stream was diverted around the northern side of the dam where the rock outcrop has been cut away, possibly to accommodate a wooden flume used to channel water into the race. At this point the race seems to have been 50-60cm wide.

The race was presumably designed to carry water to the Miner's camp at Mine Bay, although for what purpose is unknown. The most likely reason, however, is that it was used to drive a water wheel, and hence other machinery. Some water could also have been utilised in the irrigation of garden plots.

Two small prospecting adits were also recorded in the valley. The first is located about 40m east of the second northern tributary, directly below the water race and approximately 8m from the main stream (Fig. 7b). The adit has collapsed, and the resulting trench is about 10m long, 2.5m wide, and up to 6m deep. Minor copper staining is evident on the northern wall of the trench.

The second "adit" - more precisely described as an open-cut - is located about 50m east of the third northern tributary, adjacent to the water race. It is only 4m long and l m wide, and was probably excavated during construction of the race.

A third adit is described by Bartrum (1921 p. 127) as being "up a ril l entering Mine Bay Creek from the north about 15 chains upstream from its mouth", a position similar to that of a dike labelled "New Lode Felstone" on Hutton's (1869) map. However, despite a search in this area, no adit was located.

There may also be a fourth adit further upstream, since Henderson (1931 p i 1) refers to one situated about "60 chains from the sea". However, his description of it almost fits that of the collapsed adit near the second tributary (Fig. 7b), so he could simply have mistaken the distance.

DISCUSSION

It has been assumed here that all of the archaeological features are contemporary i.e. they relate to the mining of copper between 1842 and 1867. There seems little doubt that most, if not all, of the prospecting adits date from this period, and also the building and nearby features, but there is a remote

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possibility that the water race in particular was constructed some time after 1867. It is possible, for example, that a few of the miners continued to live at Mine Bay after mining ceased in 1868 (?), and existed by fishing, farming or growing crops. A factor which militates against this idea, however, is that construction of the water race would have involved a considerable amount of labour, and also substantial cost. The question of when, and by whom, the race was built may only be answered by a detailed study of historical records.

Fig. 7. Sketch plans of A: water race tunnel, and B: collapsed prospecting adit, Village Creek. (See Fig. 1 for location of features).

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REFERENCES

Bartrum, J. A. 1921. Notes on the geology of Great Barrier Island, New Zealand. Transactions of the New Zealand Institute 53: 115-127.

Gregg, R.C.; Petrie, J .M.; Carlson, J.R. and O'Connor, A.P. 1970. Geological report on the north end of Great Barrier Island. Unpublished report, Layton and Associates (NZ) Ltd. NZ Geological Survey mineral exploration report MR 482.

Henderson, J. 1931. Great Barrier copper mine. NZ Geological Survey 25th annual report: 10-12. Hutton, F.W. 1869. Report on the geology of the Great Barrier Island. NZ Geological Survey

reports of geological explorations 1868-9: 1-7. Moor, C. 1987. Early settlement of Port Fitzroy, Great Barrier Island. Private publication. (Copy

held in Auckland City Library). Williams, G.J. 1965. Economic geology of New Zealand. Proceedings of the eighth Commonwealth

Mining and Metallurgical Congress, vol 4: 176.

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