THE WETHERSTONES CEMENT.

Evening Star, Issue 4894, 7 November 1878, Page 4

THE WETHERSTONES CEMENT.

known by this misleading; name, and. whioh for the time has obtained celebrity from the discovery that it contain# payable gold, is a portion of early tertiary deposits abundant over a wide area in Otago. Jt ■ ik found in patches, dotted over abelfof primary schists extending from the borders of Canterbury, at i Lake. "Wanaka, in a south easterly direction} to the ocean, and near coast is in many places covered by more recent tertiary deposits of sandstone and basalt. If pi-actkal inuiers exercised their powers of observation, aiid noted and communicated their observations so that the results could be digested by scientific men such as Captain Hutton, more would thus be learned of the geology of Otago in a year than the most elaborate geological survey could obtain in many. So far little is known either of the real extent or character of these deposits, and but for the discovery that they contain gold such knowledge would be of little practical value. The deposit occurs in patches oyer the tract above mentioned, varying from a few square yards to many square miles in area, and sometimes resting in hollow's on the ■ tops and slopes of the mountains, and with equal frequency found occupying deep erosions in the lowest valleys. Tke patch at the Blue Spur approximates to a circular form, is about 150 acres in extent, and, filling the bed of a depression about 100 ft below the level ef Gabriel’s Gully, rises into a dividing ridge about 300 ft high, which is fast disappearing under the labors of the miner. The deposit bears indications l of having betn deposited in strata or beds tolerably regular and sloping at an angle of about fifteen degrees from north-west to south-east. Some of these strata consist of boulders and coarse gravel, others of beds of fine sand and clay, the latter occasionally containing small seams of lignite. The coarser material contains .the most gold, as might be expected, for assuming that the material has been brought there by fluvial action the gold and coarser material would 1 e brought down in time of flood, the 'gentler currents depositing the sand, mud, and vegetable matter. The labors of the miner have discovered by exploring the bed rock that great dislocations of the strata have taken.place since the deposit of the cement, numerous fault# or hitches being traceable extending through the superior strata and being marked by steps m the bed rook varying from a few inches to many feet in height. The sides of the hollow slope at an angle of from i’Odeg. to 30deg. towards the .centre, and present the appearance of having been ground down smooth. So remarkable is this, that on the northern slope the bed rock when first uncovered presents an uniform plain surface, sc smooth and slippery as to present no-hold for the foot. Captain Hutton suggests that the original hollow was scooped out by glacial action. The Wetherstones cement, ' which fn all respects resembles the Blue Spur, except that it is not heaped up into a mountain ridge, lies in a trough-shaped depression, extending from the slope of the ridge dividing Wetherstones and Gabriel’s, up which ’it extends for a considerable 'height, extending across Wetherstones Flat, crossing the railway, and extending for some distance in a .outh-easterly direction. Its exact limits ai e not as yet known. Tracts of cement are met with extending down to Waitahuna; but most probably they will be found to be detached patches or outleads. Most of the claims at present taken up sre on the slope of the hills and the flat below the township of Wetherstones '1 he path is now barred by freeholds, and mo doubt those will become of great value to the - owners as discovery advances The all important question is, how mu<;h and what portions of this deposit are auriferous, aUd past observation and experience affords some general principles which may be of a little service. In the first place, it is well known that all the alluvial gold in the district has beeu found on, or adjacent to, the cement. It is true that go.d was found throughout nearly the whole length of Gabriel’s and Munr ’s Gullies deposited on the schist; but few doubt that the greater part of it was produced from the erosion of the cement, and carried down the gullies during the ages that have elapsed since its deposit. As its great specific gravity, is seldom carried far from its matrix, It seems highly probable that the richest cement wi'l be found near the places where the alluvial deposits were rich. Another general rule, whioh every miner.will admit, is that the richest deposits are everywhere found in the lowest ground. This arises from the great specific gravity of the gold—for instance, if a piece of gravel or clay be thrown into a pool of water the gold will inevitably be first at the bottom, and so the gold will be found underneath. Even when loose dry washdiit is poured into a heap it will be found in washing that a larger proportion of the gold is obtained from the bottom of the heap. It is therefore exceedingly probable that the deeper parts of the trough or hollow in which the Gabriel’s cement lies will ultimately be found to be rich. Of course it is well known that in the bottom of the depression there will be found exceptionally deep hollows which will contain little or no gold. It is no doubt in one of these that the deep shaft was sunk. But this is capable of explanation, and does not interfere with the general principle. Everywhere throughout the formation beds of fine sand and clay containing lignite will be found, and from these little or no told will be obtained. There are not sufficient ata yet obtainable to. enable anyone to form a theory as to how these tertiary beds were originally deposited. They do not seem to have been eroded to any very great extent, otherwise far larger deposits of aim vial gold would have been produced than even the wealth of Gabriel’s Gully. The patches occur in all forms, the one at Wetherstones being about three-quarters of a mile in width by several miles in length. Without doubt there has been great local disturbance which has elevated some portions of the rock and depressed others and in this way effected changes in the original level. It might be of great service in the future if those engaged in mining would-take the trouble of noting anything they observe. In all probability similar , deposits will be found in other localities