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Report on the Geology & Gold Fields of Otago

Other Minerals. — Occurrences of Copper Ore, Grey Antimony, Cinnabar, and Brown Coal

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Other Minerals.
Occurrences of Copper Ore, Grey Antimony, Cinnabar, and Brown Coal.

Copper Ore.—Of this ore, two occurrences were mentioned to me as worth inspection, viz.: at Waipori and Moke Creek. Learning, however, on further inquiry, that at neither place anything of the deposits could be seen on account of the workings, through having for years been neglected, being quite inaccessible, I did not think it advisable to spend the time in visiting the respective localities. I collected, however, from trustworthy sources, the following information about the two ore finds:—

Waipori.—According to Mr. Hill, the manager of the O. P. Q. Company, a large patch of cupriferous gossan was observed in the bed of the Reedy Creek, at a point about five miles south-west of Drummond’s station. On working this patch, it led to a vein of yellow ore, one or two inches thick, running with the creek, east and west, and dipping north at one foot in eight feet. The prospector’s sunk a hole to the north in the creek bank, about 20 feet deep, when they struck the ore vein on the underlay nearly 12 inches thick, and showing fine smooth walls. A flood soon after covered the workings in the creek several feet deep with mud, whilst the shaft fell in, and the place has not been touched since; but there is still a lot of the broken ore lying about on the creek bank. Assays of it have produced from 8 to 24 per cent. of copper. The rock in which it occurs is phyllite. As ores of this class, found within auriferous districts in Victoria, have on assay proved to contain at the rate of several ounces of gold per ton, I gave a specimen of the above ore to Professor J. G. Black, the Provincial Analyst, for assay, and he kindly sent me the following report:—

"This was a sample of copper ore—copper pyrites—averaging 12 per cent. of copper. It was examined for gold, and found to contain that metal in very marked quantities, though from the small weight of the sample sent—six ounces of ore—I was not able to make a quantitative determination. A larger quantity, say 20 lbs., of average quality should be sent for assay."

Considering the character and increasing thickness of the vein, and that the ore, accerding to the average of the assays made, might pay to work, if easily procurable in quantity, I think the vein derserves a further trial, mote especially for determining its extent and behaviour in strike.

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Moke Creek.—Mr. D. Mackellar, the secretary for the gold fields, who examined this place, could only find in the line of the old workings, situated close to the creek, thin seams of malachite and yellow ore interlaminated and small particles impregnated in micha schist, which forms the rock formation of the locality. On the opposite side of the creek a more lode-like looking formation, of 1-1½ feet thick, of gossan ore, crops out just a foot or two above the level of the water, dipping apparently downward in strike; the latter being N.W. and S.E., and the dip slightly S.W. Pieces of native copper, several ounces in weight, have been found in the creek below the place, According to Mr. Bradshaw, of Dunedin, the old workings followed a lode of solid yellow ore, 3-5 feet thick, of which assays by Dr. Hector and himself gave 22-24 per cent. of copper, whilst Mr. Hacket, who examined the lode on behalf of the Government, estimated it at 12 per cent. on the average. This ore, of which I saw a large lump, in Mr. Bradshaw’s office, is also like that of Waipori—an intimate mixture of iron and copper pyrites, and contains likewise some gold, according to the following report, kindly furnished to me by Professor J. G. Black, of an assay he made of a specimen I gave him, viz.:—

"This was a sample of copper pyrites, ranging from 5 per cent. to 19 per cent. of copper. It was examined for gold with positive results. The quantity analysed was too small, being only 13 ounces, to determine the per centage of gold. The quantitative analysis showed that gold is present in very marked quantities. Another sample, 20 lbs. at least, should be sent for assay."

Taking into account the quality of the ore, and relying on the statements as to the thickness of the lode left in the workings; as also, that limestone for flux and fire-clay occur in close vicinity, and fuel is not far off, I do not see why this lode should not pay for working, and it seems strange that it should have been—and for so long—neglected.

Grey Antimony.—The two principal occurrences of this ore I was told of, are—One about six miles N. W. of Waipori; the other on the top of the Carrick Range. Hearing on enquiry that the Waipori one is situated in a place so difficult of access, that carriage expenses alone would nearly absorb the value of the ore at the ruling market prices, in fact, that it would never pay to work, except with railway accommodation near at hand, I did not spend time in visiting it. The ore is said to occur, similarly as in Victoria, in bunches running in a lode-like way for a long distance, some of the bunches being 5 to 6 feet wide. According to specimens I saw, it is of a very fine quality, and should fetch the highest market price. There seems also to be a considerable quantity of yellow oxide of antimony (Cervantite) to be associated with the sulphide ore.

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Buchan’s Antimony Lode, Carrick Range.—This lies about 1½ miles east from Carricktown, very nearly on top of one of the highest spurs of the Range, about 580 ft. above the nearest gully. It strikes E. 15° S., and dips northward at an angle of about 55°. Although only superficially opened in a few places, it is traceable for over a mile in length round the top of the range towards Carricktown, and also some distance down hill. Its thickness varies in the workings from 6 in. to 2 ft., and, as Mr Buchan, who kindly showed me over the ground, informed me, one block of solid ore was worked out weighing above 3 cwt. In parts of the lode exposed, the ore is, however, rather poor, being quartzose and mixed with impure oxide. As Mr Buchan found gold in the casing, I think there is, as in similar lodes in Victoria, every probability of the lode proving auriferous, wherever quartz makes its appearance in some quantity. It is very favourably situated for being opened in strike at great depth by an adit-level from the western slope of the mountain, and a short adit to prospect it, at 40 to 50 ft. in depth, could also easily be put in at right angles to its strike. A deep adit from the eastern side of the range, which, I understand, has been under consideration, would, I think, be both inadvisable and premature. For, although the lode is a promising one, the expense of carriage of the ore to the nearest market would be so high as to leave but a small, if any, margin for working expenses out of the price obtainable for it. Only in case of its proving payably auriferous, for which, I think, there is some chance, the putting in of a deep adit would be warranted, but then it should take place as just indicated from the western slope of the mountain in the line of strike of the lode.

Cinnabar.—A discovery of this valuable quicksilver ore in some quantity in the neighbourhood of Waipori was made known nearly eight years ago, but the place having been entirely neglected since, very few persons knew about it, and it was only after much loss of time that, from directions received, Mr. Hill, the manager of the O.P.Q. Co., who kindly acted as my guide, was able to find it. The site is a deep narrow gully about three miles south of Drummond’s Station, in the centre of very broken country, at the foot of the Waitahuna Heights. The gully has been worked for gold, and the cinnabar, in small grains, and occasionally larger pieces about the size of a bean, was obtained in washing the stuff. The point which yielded most of it is near the head of the gully, and there some eight holes have been sunk in angular quartz and schist drift up a depression in the bounding range. From these holes—now all collapsed-which apparently ranged from 8 to 16ft. in depth, samples of several pounds in weight are said to have been obtained. On closely searching the spoil heaps round the holes, I could not, however, discover any traces of the mineral. Reports say that the few men who worked at this spot could easily have page 187washed out 5dwt. of fine ore in a week; but, if such were the case, it seems strange that they should not have done so, as the value of hat quantity would have well repaid them for their trouble. As cinnabar, though in less quanity, has been found for miles around this place, in nearly every gully worked for gold, it may either, like the cinnabar of Mudgee, New South Wales, have been formed in the drift itself—a very rare occurence—or have been derived from the denudation of thin veins in the crystalline schist surrounding. And this latter origin I consider the most likely, judging from numerous occurrences of the kind in Europe. Very few of these, however, have, even with cheap labour and under other favourable conditions, proved payable to work; and I do, therefore, not think that the place under notice deserves to be farther prospected, more especially as local circumstances would render this work, if properly executed, very expensive.

Brown Coal.—In consideraation of the high value the occurrence of this fuel is for the Province, I visited several of the mines within easy reach during my journey, and made the following observations:

Shag Point Coal Mine and neighbourhood, Palmerston.—This mine, situated within a few chains from the sea shore, is on a fine seam of first-class pitch coal (the best kind of brown coal) 7 to 10ft., in places 12ft. thick, which dips at the rats of about 1ft. in 10 N. E. towards the sea, and rises into the Shag Point hills at the Back—the field available for working being indeed very large. It has been opened, and is being worked by a fine adit, and the system of exploitation adopted is by "post" and "stall," the stall being taken 14 to 16ft. wide, whilst the pillars left between are only 7 or 8ft., a thickness which appears to me rather small to insure the safety of the mine; for there is the danger of the front pillars being crushed long before the stalls have been wrought to the farthest end of the field. Below this fine seam, with a stratum of 4ft. of shale between, there is another seam of similar good coal about 4ft. thick, which has not as yet been worked. Walking along the beach this lower seam can be traced for a considerable distance to a point close to the mouth of the Shag River, where it disappears towards the sea in consequence of a roll or saddle in the strata, well exposed on the cliff, changing the dip to W. 25° N. at angles varying from 25° to 45°. Round the cliff up the Shag River, which runs close at foot, a series of six seams crops out through a distance of 5 or 6 chains, and there may be several more higher up the valley towards Mount Puke Ivitai. Some of these seams are several feet in width, and their basset edges can clearly be seen across the river, disappearing underneath the sand hills of the flat beyond, their dip being at an angle of about 35° seaward. As there is a considerable breadth of ground between the shore line and the line of strike of the seams, from the river across the flat, page 188there is no doubt some chance of a certain extent of the seams existing and being workable in the lower end of the flat above high water mark. All depends upon the depth of the valley, respectively to the thickness of the overlying sand and drift deposits. If these latter are very shallow throughout, the coal ought to exist underneath, the whole of the above area; whilst on the contrary, if their thickness is very great, there is little or no chance for it at all, for in that case the slope of the valley formed of the coal rocks would be correspondingly steep, and the seams would run down it towards the sea, probably without curving round into the flat, outside high water mark. Mr Rich, the enterprising proprietor of Bushy Park, who kindly conducted me over the ground, told me he intended to risk some money in prospecting for the seams in the flat by sinking and boring; and he may by this time have already solved the question as to their existence at a spot we agreed upon as the most suitable to commence operations. Whether the seams, if found, would pay to work, is a rather doubtful point, however, considering the large quantity of water that may likely exist in that part of the valley, representing, as it does, the embouchure of a pretty large river.

The Real Mackay Coal Mine and neighborhood, Tokomairiro.––This mine, kindly shown me by the fortunate proprietor, Mr. Mackay, is opened upon a splendid seam of pitch coal, about 21 feet in thickness, of nearly as good a quality as that of Shag Point mine. It (the seam) is solid and pure throughout, as far as exposed—a distance of about 2½ chains, and dips at an angle of 4-5° towards W. 20° N. The workings, consisting of an irregular quarry, are situated on the side of a low flat-topped hill, dividing two gullies, and of which the seam no doubt forms the base throughout, being overlaid by an increasing thickness of sand and fine clayey gravel. But even right on top of the hill this overburden would probably not exceed 20 feet in depth; at present it amounts to about 10 feet. The quantity of coal available for remarkably easy access is extraordinary, and if working were carried on more systematically, the working expenses per ton might be reduced to perhaps less than half of what they are at present. For instance, instead of throwing the overburden down the face on to the floor of the seam, and moving it from there once or twice over, as I saw being clone, a tramway ought to be constructed from the top of the seam into the gully close in front, on which it could be at once trucked out of the way. In the breaking of the coal, more care should be exercised in order to produce a less quantity of smalls than at present; and a more advantageous method of working would be by side stopes, similar to the Long Wall system, with small tramroads leading from the stopes to filling places for carts, &c. As far as observable the seam extends into the hills all round the mine, but apparently becomes thinner and page 189dips steeper the further away from the latter. At one place, some five chains eastward, it has been sunk upon and found only about twelve feet thick, but of fine quality, with thin seams of jet running through it; whilst some 16 chains to the N.E., where it is plainly exposed up the side of a hill, it is reduced to about 6 feet, quality unaltered. A local company is here opening it, at a spot well chosen near the foot of the hill, by an adit at present 40 feet in length, and with the object of working the seam in the proper manner up its dip. But they had already worked out an apparently large portion of the seam in a very disadvantageous way down its dip, and at an unsuitable place some distance up, and in a sharp depression of the hill; for every bucket of coal and probably also of water, collected under foot, had hereto be raised up the incline and the coal carted down the hill to the point, where the seam is now being—and should originally have been—opened. There are several other places on the flanks of the surrounding hills, where coal has been prospected and slightly worked; whether these are on the seam just noticed or on different seams, requires yet to be determined. Considering the extent, easy accessibility and quality of the coal already disclosed, irrespective of the chance of other seams existing, its neighborhood to the railway, &c, this locality may likely become one of the most important sources of supply of the fuel for the Province.

Brown Coal Mine, near Lawrence.—This lies about ½ mile west of south of the town, and the deposit—an earthy brown coal—seems to occupy a small trough or basin. For where opened its dip is a few degrees south of east at an angale of 15 to 20°; but another outcrop, about ½ mile beyond, on much higher ground, dips in the reverse direction., thus proving a fall from both sides towards the centre. It was first opened by an incline, but is now worked by a fine roomy shaft and horse whim. Its thickness is at present 17ft, and seems to increase towards the centre of the basin; but only 10 to 12ft. of the bottom part are taken, in order to secure a good roof of the remainder—very little timber being in this way required for support. Although the coal, as an earthy kind, is of but a middling quality being laminated and falling easily to pieces on exposure to the atmosphere, still, as it burns very fairly, giving out a good heat, it is of high importance to the district, and duly appreciated for household and other purposes. In some places in the deposit it is rich in resin, and its quality seems much to improve towards the centre of the basin. Judging from its general character, I think this coal would be well suited for being compressed into briquets. The deposit is overlaid by a stratum of fine fire clay, which is manufactured in to first-class bricks at the mine.

There are several more deposits of brown coal of generally good average quality, worked higher up the country, for instance, between Roxburgh and Alexandra, at the foot of the Carrick Range, page 190between Cromwell and Arrow, in the valley of the Kawarau, etc. These I had no time to visit, and can only say that lying as they do within districts entirely bare of timber for fuel, their occurrence proves an inestimable boon to the inhabitants. Judging from their sites, as pointed out to me, I think there is every probability of numerous other deposits of the kind existing in the old lake basins in that part of the Province.

Down country, near the seaboard, the occurrence of some fine deposits of the fuel is hardly of less importance; for instance, of the Green Island, near Dunedin, and of Kaitangata, the coal of which latter, judging from specimens, would seem to rival that of Shag Point in quality.

In Bohemia, and some parts of Germany, more especially Westphalia, brown coal occurs in abundance, and it is consumed in immense quantities, not only for household purposes and common steam engines, but also, compressed into hard briquets, for locomotives, and even for gas-making. Regarding its use for steam engines, several inventions have there been made in the construction of fire-places for the boilers, which greatly enhance its heating effect, whilst being easily attended to, and not very expensive, and such an improvement in the mode of burning the fuel would be worth introduction, or certainly at least a trial in the Province, I attach a drawing of a fireplace of this kind—the so called "Treppen Rost’ or "Step-furance"—most approved of in Germany, and give in appendix 13, full particulars regarding its construction and mode of working.

In herewith concluding this report, I beg to return my cordial thanks to Mr. Mackellar, the Secretary for the Gold Fields, for his urbanity, and the kind and valuable assistance he afforded me in my work during the time of our joint travel, and to state that I found on the part of all—whether engaged or interested in mining—with whom I came in contact, an earnest desire to further, in every way, the object of my visit. In the subsequent descriptions of the reefs, I have given the names of those who principally aided me in my examinations; whilst I beg here especially to acknowledge my indebtedness to Mr. L. O. Beal, Captain Hutton, and Mr. H. J. Cope, for much valuable information and advice they imparted to me on many subjects comprised within the scope of this report.

I have, &c.,

George H. F. Ulrich, F.G.S.,
Consulting Mining Geologist and Engineer.