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The Pamphlet Collection of Sir Robert Stout: Volume 2

Report by Dr. Hector Relative to the Collingwood Coal Mine

Report by Dr. Hector Relative to the Collingwood Coal Mine.

In continuation of my former communication of 3rd December, I have the honour to report that I again inspected the Collingwood Coal Mine on 16th April, and found that the tunnel was excavated for a distance of 230 feet from the entrance, the new contractors having driven 113 feet in ten weeks. The rock continues to be very hard and tough, and only a few shale partings have been met with to favour the work. The lowest of the seven seams of coal was cut at 165 feet, and affords indications of a favourable change in the formation as it dips into the hill. At the outcrop, on the face of the waterfall, this seam only showed 6 inches of clean coal, distributed in thin layers through about 4 feet of sandy shale; but in the drive it showed 14 inches of clean coal, with a roof of sandy shale, and resting on a sandstone hand 2 feet thick, beneath which is a second seam of coal 6 inches thick. In the shale roof there is a band of ironstone 10 inches thick.

At 200 feet several small cross-joints were encountered, from which water gushed with considerable force, greatly impeding the work and adding to the cost, by frequently causing the charges to miss fire. To overcome the difficulty, I recommended the use of dynamite instead of gunpowder, as its explosive properties are not affected by water.

The drive continues to be straight and at right angles across the page 31 strata, which show a tendency to flatten, the dip having decreased from 20° to 17° as the drive advanced.

Ventilation is effected by a very ingenious contrivance erected by the manager, Mr. Marshall. Water is led from a stream above the mine, with a pressure of 120 feet fall, in a small tin pipe, and delivered through an open pipe into a cask at the mouth of the mine. Air is carried into the cask by the force of the jet of water, and by a simple arrangement is forced into a 7-inch square trunk or wooden pipe, that leads it to the working face, where it escapes with a blast sufficient to blow out a candle at 6 feet distance. The drive is thus thoroughly cleared of the powder-smoke and foul air without the usual expense of an extra hand to work a fan.

I may state that this ingenious plan was suggested by Mr. Moutre, in Nelson, who in this manner employs the high-pressure water supplied to him in Nelson to blow a forge.

A new coal seam has been found cropping out in the gully about 30 feet above the first seam, so that it will be cut at about 260 feet. It is about 6 inches thick, and on it rests a foot of very superior ironstone.

So large is the amount of carbonaceous matter distributed throughout the ferruginous sandstones excavated in the drive, that the spoil-heap in the gully caught fire, and burned with such vehemence that it was only extinguished after some difficulty by turning the creek into the flaming mass. It is therefore very probable that many of the carbonaceous layers that would not be worth working for the clean coal they contain might yet be profitably worked along with the bands of ironstone for the supply of a blast-furnace.

The elevated position of the mine, with its coal and ironstone seams, and the close proximity of fine crystalline limestone, which is cut through by the tramway between the top of the incline and the mine, are all favourable circumstances for the establishment of ironworks at this place, as the furnaces could be charged with the raw material, and manufactured iron delivered by gravitation at a favourable place for shipment. Having mentioned this to Mr. Webster, the legal manager of the Company, he applied for information respecting the cost of erection of suitable furnaces, and in reply received the appended estimate from a correspondent in England. (Enclosure A.)

Samples of the iron ores which occur along with these coal seams have been analyzed by Mr. Skey:—
1.From the coal and ironstone band, which is the highest bed in the series proposed to be cut in the tunnel, a specimen of compact brown or hydrous hematite was found to contain 46.06 per cent, of iron. The ore occurs in quantity immediately over the main or 3 feet 6 inches seam of coal, and is mixed with a large proportion of carbonaceous matter in irregular layers.
2.Concretionary ironstone from below the main coal. This is really a highly ferruginous shale, about 2 feet thick, but in two layers, separated by 1 foot of coal. The concretionary structure is only discernible on weathered surfaces. A fair average sample of page 32 the ironstone gave 43.26 per cent, of iron. Both of these ores contain a good deal of iron-carbonate disseminated throughout.
3.From the ironstone already mentioned in this report as underlying a newly-discovered coal seam low down in the series.

The coal is only 1 foot thick, and the ironstone is about 16 inches; but its full thickness and relation to the other strata will not be known till it is cut in the tunnel, in which it should be reached at about 270 feet. The ironstone is very compact, and from the large proportion of carbonaceous matter intermixed, and from its containing carbonate of iron, could be easily smelted. The per centage of iron it gave on analysis was 42.1.

Several other rich iron ores are found in this district, though not immediately connected with the coalmines. Thus, along with the graphite seams in the Ruataniwha and Pakawau, and on the Otamataura Creek, red hematite ore is found, though a solid vein has not yet been discovered. A rolled fragment from the last-mentioned locality has the following composition:—
Sesquioxide of iron 88.3
Siliceous matter 10.5
Water .8
Loss .4

The per centage of iron contained in the ore is 61.81.

Within easy reach of any ironworks established in this locality would also be the valuable deposits of brown or hydrous hematite at Parapara, which is only four miles distant This ore might be valuable to mix with other varieties of ironstone, although not well adapted by itself for the manufacture of iron of fine quality.

During the past season I have twice crossed to the western slope of the range behind the coal mine, and traced the coal measures till they sloped with the surface westward towards West Wanganui Inlet. No other rock is seen in situ but soft brown sandstone and shales; but in the creek above the mine there are large masses of a fine-grained conglomerate, which prove that there are conglomerates in the upper as well as in the lower part of the formation. On the crest of the range, at 2,000 feet altitude, the strike of the sandstones is almost N.E., with a dip of 12° to the N.W. About 400 feet below the summit, on the west side, is a 2-foot seam of bright coal, dipping 15° to N.W., the sample from which has the following composition:—
Water 4.06
Fixed carbon 58.65
Hydrocarbon 35.33
Ash 1.96
Evaporative power 7.0
page 33

This coal forms a strong coke, and is quite as useful as that from the seams in the mine; but in extent, appearance, and the high per centage of water for a bituminous coal, it resembles the seam at Pakawau.

No calcareous beds were seen in the upper part of the formation on the top of the range, as stated on the authority of Mr. Marshall in a previous report, the limestone referred to by him being only the outcrop, on the spur south of the mine of the crystalline limestone that underlies the coal formation.

Coal seams have recently been found on the face of the Whakamarama range, about five miles south of the coalmine, in the bed of the Otamataura stream, by Mr. Ellis, who guided me to the locality. We reached it by ascending a steep spur from the Aorere river, below the junction of the Otamataura, to the height of 1,800 feet, and then dropping into the valley of the latter stream at an altitude of 1,000 feet. Below this point the valley is precipitous, the stream leaping over precipices of conglomerate, being the "Ramparts" that are so distinctly visible from the Collingwood side of the valley. These ramparts are formed of the conglomerates at the base of the coal formation, the surface of which can be traversed by the eye along the face of the hills for many miles both to north and south.

There are four coal seams cut across in the bed of the stream, which exposes the following section in its course for 200 yards back from the top of the fall:—
(a) Brown sandstone, forming the upper part of the range, and almost covered with vegetation, but showing beds of rather fine gravel conglomerate, at least 1,000 feet.
(b) Coal shale ½
(c) Gray sandstone 2
(d) Coal (A) 3
(e) Brown and gray sandstone 40
(f) Coal ¾
(g) Dark Sandy Shale 5
(h) Coal (B) 3
(i) Sandstone 6
(k) Conglomerate.

The thickness from the top of the fall to the base of the formation, where the conglomerate rests on granite, was not ascertained, but it is at a much lower level than in Mine Creek.

At 100 yards up the creek, from the top of the fall, the strata are cut by a fault which throws down the coal seam to the west, as shown in the section.

The prevailing dip of the strata east of the fault is 8° to 12°, to W. 20° N., and the strike of the fault, as far as could be made out, is W. 20° S., its inclination 60° to N.W.

The existence of broken coal in the crushed fragments, included in the fault, renders it pretty certain that there are higher seams in the formation than those above described.*

Thomas Mackay,

page 34
The composition of samples taken from the above seams is as follows:—
(A) Upper Seam. (B) Lower Seam.
Water 2.19 1.36
Fixed carbon 52.89 55.61
Hydrocarbon 36.63 29.29
Ash 8.29 13.74
100.00 100.00
Evaporative power(A) 6.8 (B) 7.2

Both coals are hard, black, and lustrous, burning freely, and yielding a large quantity of coke. Their powder is brown, and in both iron pyrites are disseminated in minute quantities, giving to the ash a pale buff colour. The upper coal is compact and homogeneous, while the lower is distinctly laminated.

Still further up the valley than the fault are heavy blocks of conglomerate like those already described as occurring in the upper part of Mine Creek; but as the ferruginous beds which are so prominent in the Mine Creek section are wanting, the formation must have been altered very much in character, the conglomerates at the base having thickened and replaced much of the proper coal-measures; on the other hand, the coal seams must correspond with those on the western slope of the mountains above the coal mine, and other seams of coal may yet be discovered lower down the valley.

In the event of workable seams being found in this part of the field, access to them will be obtained by the valley of the Otamataura Creek, by the employment of inclines, the circumstances being similar to those in Mine Creek.