H.—34.

beyond the present dip-clrive. What is more significant, the seam has definitely diminished in thickness towards the south from an average of 20 ft. at the north of the present workings to, at most, from 7 ft. to 10 ft. This is the largest coal-bearing block so far proved in the whole Grey field, and it is unlikely that any block will exceed this in areal extent and simplicity of structure. The amount of proved coal in the Kimbell and Morgan seams, as at present developed, is estimated at 4,000,000 tons by the manager, Mr. A. Smith, and of this about 50 per cent, will be recovered. To this must be added the estimated 6,000,000 tons recoverable from the new James Extended, giving 8,000,000 tons of recoverable coal that the State Mines Department can confidently rely upon. The co-operative mines can work only those comparatively small blocks favourably placed for transportation, and consequently they are situated along or close to railway or road. These are blocks that have been faulted or folded into such a position that no costly development-work is necessary for their exploitation. The most accessible of these are now being mined, and in a few years will be exhausted. From the foregoing, and from Mr. Morgan's considered statements, it is manifest that the resources of the Grey field must be conserved. How this may best be accomplished can be determined only after an exhaustive investigation of the whole field, and this entails an extensive boring programme. Two avenues suggest themselves. One is that the field should be developed as a unit; the other is that the possibility of mining stony seams, and of subsequently extracting the stone and washing the coal, should be investigated. All the coal from any one area should be recovered while transport facilities are available and before the major seams of that area are exhausted, for in most areas it will not be possible economically to re-establish the transport system and to recover patches of coal that remain. Operations in one area should not be conducted so that in extracting coal from one seam the coal in an overlying seam is lost for ever through the country caving. It cannot be too strongly emphasized that on present prospects problematical areas where coal may exist at considerable depth, thin seams, or remnants of thick seams in remote localities, and seams with a considerable admixture of stone and dirt, all regarded as valueless at present, soon will be all that remain of the coal in the Grey field. Much coal is lost in mining some of the large seams through stone bands interbedded with the coal rendering the seam unworkable, not on account of the cost of mining the coal and stone, but because there is no economical method of treating and separating such a mixture. Again many patches of coal contain bands of " holing dirt," a fissile highly carbonaceous shale, some of which finds its way into the marketed coal. There is quite a possibility that much of the coal at present lost in the stony areas could be recovered if a suitable treatment and washing-plant were available. Not only does this apply to areas in the State mine, but also to seams that can never be worked unless such treatment is possible. It is imperative at some future date, if we are to rely on our bituminous-coal resources for domestic consumption, to work seams containing stone and dirt bands, and the time has arrived when consideration should be given to this aspect as a possible means of conserving our resources. The economy of mining coal-seams containing stone, and subsequently washing the coal, is one that will present difficulties peculiar to New Zealand. Faults and Structure. Just west of the main divide from the junction of Edward Ridge with Tom Ridge, southwards towards Mount Davy, two sub-parallel faults strike slightly east of north, and enclose between them an elongated block averaging 5 chains across. This block, which is here called the Will Block, extends from Otto Creek, west of Will Ridge,, south into the upper Davy Creek, where the two faults are 20 chains apart. An abrupt change in dip of the even-crested dip-slope at a point about 45 chains south-west of Trig. G, on the ridge south of Davy Creek, probably marks the trace of the eastern fault. A northeasterly striking fault traverses the upper part of Davy Creek from the saddle at the head of it to the fault just described, where it is terminated against the Will Block. The western fault crosses the divide between the Seven Mile and Coal creeks roughly 20 chains north-east of Trig NN, situated on this divide. The strata of the relatively upthrown block east of Will Block dip south-eastwards on the divide between Carroll Creek and Waiomo Creek headwaters, and the tributaries of Paparoa Creek to the east. South-east of the north-east striking fault at the head of Davy Creek the strata dip south-westwards in conformity with the dip-slopes of Mount Davy Block. Within Will Block westerly dips prevail in Waiomo Creek basin and in Carroll Creek basin the strata appear to be synclinally folded. South of this the structure is imperfectly known, but the synclinal fold appears to continue to Davy Creek, with a pitch to the south. West of Will Block is the Liverpool Block, the largest comparatively unfaulted block yet mapped. On its west is Tararu Fault, which traverses Tararu Creek and cuts off the westward continuation of the seam previously worked in No. 1 section of the Liverpool Mine, the downthrow, 500 ft., being to the west. Southwards this fault strikes just west of Nos. 2, 3, and 3a sections, Liverpool Mine. It crosses the Seven Mile, 12 chains west of Goldlight Co-operative Party's bin. Broadly speaking, the Liverpool Block is a southward pitching anticline 65 chains across" on the Ten Mile - Seven Mile watershed, and narrowing to 50 chains at the confluence of Davy Creek with the Seven Mile. Here the crest of the fold is 30 chains across, and the steeply dipping eastern limb has widened to 20 chains. As a consequence, the present Liverpool No. 2 Mine workings if carried south, will ever diminish in width should the seams continue to be of economic value to this point. Minor folds and fractures are superposed on this broad anticline, the most conspicuous being the zone of folding and faulting along the Seven Mile from Tararu junction southwards, in which direction the minor folding and fracturing diminishes, ultimately merging into a minor fold. Goldlight and O'Brien and Party's mines are situated on the crest of this fold in the Seven Mile,

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