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Extracted from Supplementary Report on Class I., New Zealand Exhibition, 1865, pages 373 to 387, and 439 to 443--"Anhydrous Coals of New Zealand."
I.--BITUMINOUS COAL, KAWA-KAWA, BAY OF ISLANDS.
This coal, the geological formation of which is unknown, appeared of superior quality to any other of the Auckland coals. 1 Its color was black, but in part it was covered with brown films. Its lustre is resinous; fracture and cleavage very irregular and granular; moderately hard. It burns freely; powder and streak, dark brown and glistening; coke cakes, but does not puff up as do the Nelson and Canterbury bituminous coals. This is a great advantage where a high heat is necessary, as the draught is not likely to be impaired. It is also very porous and coherent; the ash is light red and easily blown away.
II.--BITUMINOUS COAL, PAKAWAU. 2
This is of upper secondary age, and is a harder coal than that from the Grey River, but of less brilliant lustre. It burns freely, with a smoky flame; fracture slaty along its cleavage, but across it conchoidal; powder and streak, black brown; coke, semi-metallic, caking to a very coherent mass; ash, light buff; percentage of coke, 58.36, and of sulphur, 1.04.
An examination of this coal proved it to be similar in composition to a sample from the same locality previously analyzed in the laboratory of the Otago Geological Survey.
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III.--BITUMINOUS COAL, PAKAWAU.
This coal, taken from a seam 1 foot thick, varied greatly in its composition, part of it having a black resinous lustre, and conchoidal fracture, and containing only 5.8 per cent. of ash. But the greater part, and that sample which was analyzed, is a very hard dull earthy coal; fracture, slaty; powder, dark brown; coke dull, coherent, hard; ash, light grey; percentage of coke, 63.2.
IV.--BITUMINOUS COAL, BULLER RIVER.
This specimen represented a single seam 9 or 10 feet in thickness. It is a pitch black lustrous coal, compact, but easily pulverized; burns freely, with a smoky flame; fracture splintery; powder and streak, dark dull brown; coke dull, coherent, puffs up slightly; ash dark buff, easily blown away. The percentage of coke is 65.85; that of sulphur, 1.20.
V.--BITUMINOUS COAL, BULLER RIVER.
This coal is singularly free from impurities, and from its external appearance and composition evidently bearing a close relation to the column of coal from the same locality. This sample was not quite so lustrous as some of the Grey River coal, but it had a glistening appearance on certain cleavages. Its fracture is rhombohedral. It easily pulverizes to a brown powder, and yields 58.0 per cent. of a very porous semi-metallic coke. The ash is light buff.
VI.--COAL, BULLER RIVER.
A dull black looking coal; the powder, however, presenting a glistening appearance. It is tolerably hard and compact.
The coke is semi-metallic in lustre, very porous and hollow, possessing little coherence. The ash is white. The yield of coke is 67.40 per cent., and its specific gravity from 1.160 to 1.250.
VII.--BITUMINOUS COAL, BULLER RIVER.
This is rather a friable coal, easily pulverizing. Its lustre is brilliant, and its powder has a slight shade of brown, though the coal in bulk is black.
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The fracture is conchoidal. Color of ash white. When heated in a closed crucible it puffs up to a hollow ball, and leaves, on a continuation of the process, 67.84 per cent of semi-metallic coke.
VIII.--BITUMINOUS COAL, GREY RIVER.
The beautiful iridescence exhibited by this coal when broken in the direction of its cleavage recommended it for analysis. It appears to be due to the presence of thin films of a white opaque salt.
The cross fracture is black; lustre, resinous; powder and streak, dark brown; coke dull, puffs up a little, coherent; ash, gray. The percentage of coke is 64.22.
IX.--BITUMINOUS COAL, GREY RIVER.
This is a beautifully bright clear homogeneous coal. The fracture is generally uneven; in parts, however, plain surfaces are displayed. Its powder is brown, the ash white, and does not appear to have the least tendency to clinker. Ignited it burns freely, evolving a good flame, and coked in the usual manner it swells up considerably to a porous coherent mass, leaving about 61.20 per cent. of semi-metallic coke.
X.--BITUMINOUS COAL, GREY RIVER.
A coal similar in appearance to No. XI., but having a greater quantity of ash present. Powder and streak, brown; ash, white. It gives a dull looking coke, which puffs up to a very great extent.
XI.--BITUMINOUS COAL, GREY RIVER, CANTERBURY.
A very compact coal of secondary age, difficult to pulverize. Its color is black; lustre dull. The fresh fracture, however, has a glistening appearance. It possesses a slaty cleavage. Powder of coal, black; ash, light brown. The coal puffs up slightly when heated, and gives 68.37 per cent. of metallic coke.
XII.--BITUMINOUS COAL, MALVERN HILLS.
A hard black glistening coal, and burns freely with a smoky flame. Fracture, uneven; powder, dark brown; streak, brown; ash, white, and easily blown away; coke, dull, and puffs up greatly.
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XIII.--PITCH COAL, SHAG POINT, THIRTY MILES FROM DUNEDIN.
This, which is the freest burning coal in Otago, is probably of upper Mesozoic age. It corresponds exactly with Dr. Percy's definition of pitch coal, and may be considered to hold the same relative position among the Brown Coal series that cannel does to the true or older coals.
It is very compact; does not absorb water or soil the fingers. Its color is a brownish black; fracture, conchoidal and splintery; lustre, fatty, resinous; streak, lustrous, and gives a dull brownish black powder. It burns freely, with a rich oily flame, giving off only a slight odour, and leaving a bulky, but light argillaceous ash.
Upon distillation it gives off a rich gas at high temperature, and a large yield of gas oils, if a low heat be carefully applied. The coke is light, and semi-metallic, and its percentage 50.68, and that of the sulphur, 4.78.
This large percentage was arrived at by repeated determinations. Part of it seems to be combined with the gaseous matter, in the manner referred to already in the introductory remarks. 3
XIV.--SEMI-BITUMINOUS COAL, FROM WAIKAWA.
This is of upper secondary age, and occurs in seams less than twelve inches in thickness, imbedded in sandstone grits. It is very similar in appearance and composition to that from Preservation Inlet--color, jet black; powder and streak, brownish. It is laminated, somewhat fragile, but does not crack on exposure. Many of its cleavage planes show a dull brown color. Its coke does not cake. Ash, white; and as is frequently the case in these thin seams, its quantity is very large.
XV.--SEMI-BITUMINOUS COAL, PRESERVATION INLET.
This is of upper secondary age; the samples were procured from very thin and impure seams, and present great irregularities in their composition and external appearance. It is hard, compact and black, with a splintery cubical fracture rarely conchoidal; powder, black, with a faint brownish tinge in some samples; streak black and shining; ash, light buff; coke unchanged, and does not cake.
Owing to the varieties of character which the samples present, three distinct analyses are given.
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Further information respecting the chemical qualities of various New Zealand Coals: being the results of investigations made in continuation of those given in Enclosure A.
COAL FROM WALTON'S MINE, WANGAREI, PROVINCE OF AUCKLAND.
This coal is obtained from a seam about five feet in thickness, and, as it presents a considerable diversity of physical appearance in different parts of the seam, four samples were analyzed.
Sample I. was taken from the heap at the pit mouth in December, 1865, and was the average quality of coal obtained in the mine at that date. It is a black laminated coal with a conchoidal or uneven fracture, easily pulverized to a dark brown powder, burns freely, with a smoky flame, gives 48.70 per cent of non-coherent semi-metallic coke, and leaves a large quantity of grey silicious ash that is nearly free from iron.
Sample II. was taken from a stone band or impure layer that traversed the middle of the seam. This band near the outcrop was four to six inches in thickness, and the great difficulty in separating it from the coal--which could only be done by hand dressing--at first added largely to the expense of working the mine. As the seam was followed back from the outcrop this band has gradually thinned out, and in March last it had quite disappeared, while the pure coal had increased to a six foot seam. This band proved to consist of a mechanical mixture of sulphurous clay iron-stone with coal of the same composition as sample No. 1, the incombustible matter being as much as 44.80 per cent.
Samples III. and IV. were taken from the working face of the mine in March, 1866, where the seam presented two distinct varieties of coal.
III. formed the greater part of the seam, and is a hard compact coal capable of resisting pressure, and therefore fitted to bear transport without falling to dross. It is of a lustrous black color and traversed by alternating layers of jet and dull coal in the same manner as most of the varieties of coal from New South Wales. It contains bright films of iron pyrites and small pebbles of quartz. In other respects it is similar to sample No. I. to which its greater compactness renders it on the whole superior, notwithstanding, as will be seen from the analysis, that it contains more both of water and ash.
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Sample 4 is from a stratum in the middle of the main seam about one foot in thickness, and is characterized by extreme friability.
Being very bright and lustrous, and having a small proportion of ash and large quantity of water in its composition, it resembles jet.
It is singularly fragile, breaking in small fragments under the slightest pressure.
When on board the small steamer that plies between Wangarei and Auckland, I had an opportunity of observing this coal used for raising steam, and comparing the results obtained with those from Newcastle coal.
I had one of the three fires fed with the Wangarei coal only, another with the Newcastle coal, and a third with a mixture of the two.
The Wangarei coal was far from being a fair sample, as it contained a large proportion of the "band" intermixed with it. In consequence of this it formed a very bad clinker, which being very fusible set to a hard slag, which was difficult to disengage from the furnace bars.
The Wangarei coal gave out a most intense heat, burning with a clear white flame; the flame of the New South Wales coal being red and smoky.
About one-third more of the Wangarei coal than of the Newcastle coal was required to keep the fire in good order, but the furnace fed with mixed coal appeared not only to burn more freely but to require no larger quantity than of the Newcastle coal when used alone.
The only defect when the mixed coal was used was the formation of clinker, but this will, I believe, be much reduced in quantity in the coal now obtained from the mine.
The results I subsequently saw on board the same steamer, in March last, quite confirms me in this opinion, and I have no doubt that for coasting steamers this coal will prove a most valuable fuel.
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COAL FROM KAWA-KAWA RIVER, BAY OF ISLANDS.
This coal was analyzed and previously reported on in the Exhibition Jurors' Report page 384, (vide Enclosure A.,) samples of it having been sent to Dunedin in 1865; but since then the locality has been visited and examined geologically, and further analyses have been made.
The main seam is only visible at an outcrop in the bed of a small creek, and in immediate contact with Diorite slate; but a shaft was sunk through the seam about sixty feet from this outcrop, by which there was found to be a total thickness of thirteen feet six inches of pure coal, but broken into two or more subordinate seams by "partings" of shale and chert. The seam was also pierced by a bore at 200 yards distant from the shaft in the line of strike, and the result proved it to have varied very considerably in the order and thickness of these clay partings.
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Many other borings were made in the neighbourhood, but none were continued to sufficient depth to reach the coal, so that we have no information regarding the persistence of the character of the coal over a large area.
The geological age of this coal is identical with that in Walton's mine at Wangarei, and also with coal which I examined at Hikurangi, a locality midway between Wangarei and Kawa-kawa, and there is every reason to believe that the coal field is more or less continuous throughout a large district.
The coal from these several localities appears to be of very different qualities, however, and in the case of the seam at Kawa-kawa is exceptionally good.
From its possessing chemical and physical characters that distinguish it from all other New Zealand coals, we may expect that these peculiarities are in some manner connected with its valuable qualities, and that both are perhaps due to local causes which may have operated over only a limited area.
The mineral characters of all the specimens of the coal from the main seem are identical. It is of a brownish black color, with a marked resinous lustre, and shortness of grain, that at once distinguishes it. Its cleavage in large masses is cuboidal, but can hardly be detected in small fragments, as its structure is almost granular.
It burns very freely with a rich flame, and most intense heat. It cakes slightly, but when coked does not swell or puff up. The quantity of ash is very small, but that of sulphur large, a portion of it existing in an oxidized form.
This is a very marked peculiarity of this coal, considering that it is remarkably free from iron pyrites and the clay matter that might cause the formation of aluminous minerals on exposure to the air. As a steam and forge coal, it appears from the reports of experiments that have been performed to have a very high value, and the only objection to its use for the former purpose will be its extreme friability, as very little handling will convert it into dross.
What appears to be a second seam was discovered by Mr. Moodie in the bed of a small stream about half a mile distant from the first discovered outcrop.
The coal from this seam has the external appearance of being very inferior, and approaching more to an ordinary earthy brown coal, but on being analyzed it was found that its greatest point of
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difference was in the large quantity of ash that it contained, the percentage of water being even rather less than in the coal from the main seam.
Both the seams of the Kawa-kawa coal, and also the coal from Wangarei and Hikurangi, contain masses of retinite or fossil resin, and also quartz pebbles embedded in them, which, along with the peculiarity in the first mentioned coal, of having a large quantity of sulphur in its composition, uncombined with iron, connects the coal of this northern district closely with the common brown coals, their redeeming feature being the low percentage of water which they contain. Considered from this point of view, however, there exists quite as wide a distinction between the Wangarei coal and that from Kawa-kawa as between the Wangarei coal and the Hydrous Brown Coal from the Drury mines.
The value of the Kawa-kawa and Wangarei coal for the purpose of manufacturing gas was tested practically by Mr. J. N. Wark, the manager of the Auckland Gas Works, and the results given in his reports, which are appended hereto, show that while the Kawa-kawa coal yields the largest quantity of gas, viz., 11,660 cubic feet per ton, the yield of the Wangarei coal being only 8,500 cubic feet per ton, the quality of the gas is better in the latter case.
It will be observed, however, that the Kawa-kawa coal produces a large percentage of marketable coke, while the coke of the Wangarei coal is very inferior.
Kawa-kawa Coal--Main Seam.
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2. Kawa-kawa--Moodie's Outcrop.
REPORTS OF EXPERIMENTS AT AUCKLAND GAS WORKS.
Gas Works, Auckland,
1st December, 1865.
I beg to submit to your Honor the following experiments on Bay of Islands or Kawa-kawa coal:--
This is a coal which I think would be called a "cherry coal,"--it does not melt or cake but to a very limited extent, consequently the coke is not large but of excellent quality. It gives off the gas freely,
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and the illuminating power is about equal to that of the coal I have usually had from Newcastle. Evidently it contains more sulphur, but there is no difficulty in separating this ingredient from the gas. Therefore by comparison, although the cost of purification may be increased in respect of the Kawa-kawa coal, a larger quantity is taken off in shorter time. The residue in coke is at least 10 per cent. greater, and the quantity 20 per cent. superior.
In testing the value of any coal commercially, it is not easy to give a satisfactory approximation to the proportions of volatile matter coke and ash produced; obviously the exact quantities of tar, water, ammonia, sulphur, &c., belong to those nice arrangements of the laboratory of the chemist.
Therefore your Honor will pardon me if I have not attempted what seemed beyond my sphere. It may be observed that none of the experiments give exactly the same results. This is common: One part of a seam of coal might be superior to another, which would tell on the quantity or quality of gas or coke; or in quenching the coke a larger amount of water might be used at one than another time. This latter I think was the case in regard to at least the first experiment. The heat of the retort used was pretty equal during all the experiments, not less than what I understand to be about 1500 Fah. so to secure a good and uniform result.
I may further remark that I have tried the coal with the usual mixture of Lesmuhago, and the illuminating power seemed about the same as is usually supplied. I also tried it with about 1 in. 15 of kauri gum scrapings which I had at hand, and the result was similar.
I am, &c.,
J. N. WARK.
To His Honor the Superintendent of the Province of Auckland.
Gas Works, Auckland,
12th December, 1865.
As you have entrusted me with a quantity of coal from Wangarei, for the purpose of testing its value as a gas producing coal, I have the pleasure to report to you as follows:--
The result of the under-noted experiments shows that the coal yields about eight thousand five hundred cubic feet of gas to the ton.
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The first experiment was protracted an hour longer than the other two, because I thought the heat not up to the mark, consequently a larger quantity of gas was obtained, but the quality would naturally be depreciated. The quality of the gas, however, is superior to that of any coal that has yet come under my notice in the Colony. The quantity of sulphuretted hydrogen is, I fear, above the average. It is not a fusible coal, and the coke produced is small and friable, while the quantity is not great.
Altogether it is encouraging that a coal of so good a quality is at hand.
I am, &c.,
J. N. WARK, Manager.
To Mr. Walton.
Wangarei Coal (Mr. Walton's) 11th December, 1865.
PAKAWAU COAL, NELSON.
Several samples of coal from fresh localities in the Pakawau and West Wanganui District have been sent to the Museum, which, on the
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whole, prove to be rather superior to any that have been previously analyzed. (Vide Enclosure A.)
The first sample examined was obtained by a shaft that was sunk 46 feet below the surface, in October last, from a seam 3 to 4 feet thick.
It is hard, compact, and lustrous, and indistinctly laminated. At first it burns freely, with a smoky flame, but, after the gaseous matters are consumed, the remainder, or more than half the bulk of the coal, can only be consumed with the aid of a powerful draught. It cakes slightly in burning but does not swell or puff up. Seams of coal have now been discovered in many parts of the Massacre Bay District, and there is every reason to believe that the coal-bearing deposits are very extensively developed in that part of the Province of Nelson as well as towards its southern border, where the commercial value of the coal is now thoroughly established.
The most recent discovery in the Northern District is on the Aroere River, where a seam, at least 4 feet in thickness, has been discovered, apparently of a very superior quality of coal.
Two samples of this coal have been examined, both furnished by Mr. Wells. They are of a glossy jet black and laminated structure. Their powder and streak is dark brown.
Sample I. which is from the lower part of the seam leaves a buff colored ash, and though it cakes it does not puff up.
Sample II. is from above a "clay parting" in the seam, has a gray colored ash, and swells in coking to several times its bulk when in powder.
In both cases, as in the first mentioned coal from Pakawau, the coke burns only with a strong draught.
Details of Analysis--Pakawau Coal.
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An average sample of the coal found at West Wanganui, selected from a small quantity sold in Nelson, was also furnished for analysis by Mr. Wells. It proved to contain a larger quantity of earthy matter than is usual, and as it has only a small percentage of fixed carbon, and does not cake or form a coke, it appears to have more the character of a bituminous shale than a steam coal.
Its cleaveage and texture is, however, good, and it exhibits alternations of dull earthy coal, with flakes of pitchy lustre as in New South Wales coal. Its powder is dull brown, and its ash of a pale brown colour.
A further sample of West Wanganui coal was received from Mr. Otto Wiesenhavern, and on being analyzed gave the following results: Character--Massive, compact, hard, possessing plain cleavage in all directions; appearance generally dull, but in parts having a jet-like lustre; surface dulls on exposure, but does not break up It has thin veins of iron pyrites traversing it. The coke, which is only slightly coherent and lustrous, amounts to 54.30 per cent.; color of ash, red.
Fixed carbon ............ 50.10
Hydro carbon ..... 37.10
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HYDROUS PITCH COAL FROM KAIOU RIVER, WANGAROA HARBOUR.
This specimen, which is said to be from a very thick seam in the upper part of the Kaiou River, which flows into Wangaroa Harbour, was given to me by Henry Williams, Esq.
Although its composition places it among the Hydrous Brown Coals, from the section of the strata with which it is associated and from some of its characters, I am inclined to think it belongs to the same group as the Kawa-kawa and Wangarei seams.
In physical appearance it might be mistaken for some of the samples from the Grey River on the West Coast of the Middle Island, especially in its lustre, which is singularly bright and glistening. It burns with ease, and yields a non-coherent metallic coke. The ash is of a bright buff color. Composition:--
BITUMINOUS SHALE, AWATERE, NEAR MONGONUI.
The locality given for this mineral, of which only a small sample has yet been obtained, is on the authority of the Rev. R. Taylor, who discovered it many years ago.
Grey micaceous sandstones of upper secondary age occur at the locality indicated, and contain carbonaceous layers with plant impressions, but no seam of this substance can now be detected; however, as the cliff is being constantly worn away by the action of the sea, the original site may have long since disappeared, but, as the same mineral
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may occur in other parts of New Zealand, its properties were carefully examined.
From the composition of this mineral it will be seen that it approaches closely to the famous Torbane Hill oil shale in character, to which it also bears a considerable external resemblance, with the exception of being rather darker and more resinous in lustre. Its properties are as follows:--very coherent, close grained, hard and tough, almost elastic, does not show the slightest indication of lamina or cleavage planes, having a smooth semi-conchoidal fracture in every direction.
What appears to be the exterior portion of the stratum is of a yellow color, while the rest is of a dull black color, and perfectly homogeneous in every part.
It is exceedingly difficult to pulverize this mineral, but when a moderately fine powder is obtained it has a very decided brown or chocolate color. Its specific gravity is 1.112.
It ignites with ease and bursts into a flame which is sustained for a long time with great vigor.
The flame is at first very luminous and bright, but soon becomes long and smoky, and during combustion small oil bubbles may be seen escaping.
The presence of oil to a large extent among the volatile matters escaping at comparatively low temperatures, is best observed by heating the substance in a partially closed test tube to a temperature of 400 deg. Fah., after previously drying it at 212 deg.
The oil is then seen to condense upon the cooler portion of the tube in considerable quantity, and when finally removed to a cold place a large portion of the oily matters solidify to a white substance, probably paraffine.
When heated to a dull red heat, in a closed crucible, till no more gaseous matters are evolved, there remains about 23.00 per cent. of light non-coherent cellular and slightly lustrous coke, and this in the open fire was found to burn readily to a perfectly white ash.
In order to compare this bituminous shale with others of known value, samples of the oil shale from New South Wales, and of the Torbane Hill mineral, were analyzed at the same time, and the following table gives the results obtained, together with the composition of the several other shales from which oil is distilled, as given in Gesner's work on "Distilled Mineral Oils."
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* Those marked with asterisks have been examined in this Laboratory.
From an inspection of the above columns it will be observed that while the New South Wales and the Mongonui samples are for all practical purposes alike, and indeed might well have been taken from the same seam, they are both superior, as far as can be judged, to any of the rest, which, it may be remarked, were purposely selected for comparison, on account of their excellent quality.
It should be stated, in order that the value of these oils may be properly appreciated, that the yield of gas from the Torbane mineral is 13.000 cubic feet per ton, of a specific gravity of 0.775, the quantity of crude oil is 120 gallons, of which 65 gallons may be made into lamp oil, 7 gallons of paraffine oil, and 12 lbs. of pure paraffine.
The Breckenridge coal yields 130 gallons, 58 per cent. of which can be manufactured into lamp oil, and 12 gallons into paraffine and paraffine oil.
The Albert coal yields 110 gallons of oil per ton, 70 per cent. of which can be made into lamp oil, and 10 per cent. is heavy oil and paraffine.
These particulars are extracted from the same work on Coal Oil and Petroleum, previously quoted.
It may be noted that the coke from these bituminous shales is used as a disinfectant, being admirably adapted for this purpose from its incoherence and pulverelent structure, by which it affords a large surface. The coke from this particular sample was found to exhibit very decided properties of this kind.
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