PHOSPHATE COCK DISCOVERY

Otago Daily Times, Issue 12418, 30 July 1902, Page 5

PHOSPHATE COCK DISCOVERY

(Fnou Oun Owx CorniEßroxDExr.) [ WELLINGTON, July . 29. An advance copy of the Mines Record, which reached me this afternoon, contains references to tho phosphate rock discovery in Otago. Tho Inspector of Mines for the | southern district, reporting on the discovery pays:—" There is in all probability an extensive deposit of phosphate overlying tho limestono formation in this property, and although tho prospecting work carried out is not sufficient to enable an accurato estimate to Ihj formed of tho quantity of rock phosphato available on the north-custom portion of (ho estate, still, owing to the extent of outcrop visible, thero is practically sovoral thousand tons in sight and available for immediate treatment. Tbo deposit may be expected to extend to the few neighbouring properties carrying limestone formation, and in consequence much' interest is taken locally in regard to the announcement of tho discovery by Mr Ewing and party. As showing the littlo knowledge possessed by tho residents of the district as to tho value of the deposit, it is stated that lime burners in tho neighbourhood have thrown hundreds of tons of tlio rock aside as being useless stripping, while ploughmen have rolled boulders olf hillsides into the gullies, and tho rock has in places been broken and used for road metal,"

Hie Government geologist reports that tlio samples forwarded by tho Inspector of Alines consisted, for the most part, of rock that is part of a surface exposure, which had long boon exposed to the influence of tho weather, and thereby may have lost by solution a portion of the more valuable mineral. Tho phosphatic mineral forms a pnle-groy or yellowish-brown finegrained rock, often brccciated and frequently infiltrated by tlio products of solution and' redeposition of soma parts of tho original rock, or the secondary deposit may take a more earthy form. Ono special sample forwarded eeem3 to have been taken from sonic depth in tho ground or from, the cc-ntro of a solid boulder; Its colour is nearly white, and it is a fine-grained coinpact rock, without joints, and nowhere dis-' coloured by iron oxide, as most of .the surface specimens are. The sample analysed yielded 6.75 per cent, of silica,' which is the main impurity, the percentage of alumin and iron oxido being At. places the percentage of silica., must bo considerable, as in some of tho samples sent minuto particles of quartz are frc-ely scattered or clustered in littlo aggregations throughout the stone. The first samples obtained were-dark coloured and fossilifcrous,, containing sharks' teeth. These, may have been coprolitic in character, but there is a probability of a solid stratum of this rock boing discovered, P>eing the uppermost bed of Hie series to which it belongs, the phosphate rock is liable to have been removed at many places where the underlying limestone is yet present, and whore drilt ciay or soil deeply covers the underlying rock. It may require a considerable amount of work to prove by how v much and in what directions the phosphatic rock ha; continuity. In other parts the eastern district of Otago this rock is liable to be present—indeed,' it may -be found from. tho Kurow, in the Waitaki Valley, along'' the, coastal region to Blueskin, .and llvj neighbourhood of Dunedin. At least there is nothing that forbids its presence at many places'in tho part of the provincial district referred to. Spscial search will, however, require to bo made by persons acquainted with tlio character of the rock -ought for. The analysis o£ Dr MacLaurin shows tho presence in tho phosphate rock of some organic matter which helps us to understand its origin and original mode'.of deposition, but as it now exists it cannot be called a coprolitic nor yet -a_ bono phosphate other than containing the constituents of bones. Phosphatic nodule.?' (eoprolites) and bone deposits arc unccrfain in their distribution, and, as rich deposits, nre not likely to be widely extended. In this ease, however, we havo to do with a mineral which gives no signs of specific organic remains, the only indication being a little organio matter in tho rock itself. If distinct organic bodies exist they can only be detected by* comparatively high powers of the microscope. Tho deposit is of marine origin, and has all tho appearance ot being largely a chemical deposit in the bottom of the sea, whero quartz grit and green sand pains might mingle with and be included in it. Now that attention has been directed lo this rock, tlio Government geologist has little doubt that it will be found at other places, and ho anticipates that deposits of ovon greater value than yet discovered will bo found. In the joints of the rock specimens forwarded from the Horscshqo estate, Clarendon, fine colours of alluvial'gold are not rare. - ' i-