GOLD DISCOVERIES PREDICTED.

Southland Times, Issue 1025, 21 September 1868, Page 3

GOLD DISCOVERIES PREDICTED.

The Quarterly Journal of Science ' has the following :— " More than twenty years ago Sir Roderick Murchison made a great stride in advance of other geologists by showing that in certain cases the mineral. riches of distant lands may he predicted by means of geological data. In the year 1844, having recently returned from the auriferous TJral Mountains, he examined a collection of rocks from Australia, and from their similarity with those occurring in the Russian range,. he expressed his surprise that 'no goid had yet been detected ' in the Australian ' Cordillera.' The fact that gold had been detected (the discovery -being then unknown in Europe) is the strongest possible proof of Sir Roderick's induction being, in. a scientific sense, a real discovery; while the memoirs which he published on the subject in the years 1844-6 testify that his comparison of the two regions was not a mere .haphazard surmise, but the result of a comparison of the rocks, and the earnest belief of a geologist in the method and principles of his science. The principles as to the distribution of gold in the earth's crust, upon which Sir Roderick then relied, have undergone some alteration, but only' to show that gold is somewhat more widely disturbed that was at that time supposed. In. place of the lower siluriaa deposits being the only matrix in which gold is found in situ, which was Sir Roderick's original induction, we now know that they, are but the chief depositories of the precious metal. Wo one, however, acknowledges this extension of our knowledge of the possible sources of gold more freely than the author_of ' Siluria .' ; arid as the subject is one of great economic importance, we quote, in extenso, his most recent conclusions, (p. 472) : — 1. That, looking to the world at large, the auriferous veinstones in the lower silurian rocks contains the greatest quantity of gold. 2. That where certain igneous eruptions penetrated the secondary deposits the latter have been rendered auriferous for a limited distance only beyond the junction of the two rocks. 3. That the general axiom before insisted npon remains, that all secondary and tertiary deposits (except the auriferous detritus in the latter) not so specially. affected never contain gold4. That as no unaltered purely aqueous sediment ever contains gold, the argument in favor of the igneous origin of that metal is prodigiously strengthened ; or, in other words, that the granites and diorites have been the chief gold-pro-ducers, and that the auriferous quartzbands in the palaeozoic rocks are also the result of heat and chemical agency." The question of the existence of gold in Nature in other than the metallic state is one upon which various and very conflicting opinions have been expressed, yet up to this time the evidence on both sides has been of the most satisfactory character. The subject has been very fully treated of .by Professor A. . L. 3?leury, of New York, in a paper read before the Polytechnic Association of the Academy of Arts and Sciences in New York ; he observes that we do in our laboratories, metallurgie, and manufacturing establishments nothing else but attempt to imitate Nature, we have succeeded in preparing artificially a vast number of chemical combinations of gold with otherelements, but still persist in denying to Nature the same privilege. We need only look and search for- truths in 'th c book. of Nature and will, find them ;-- our test-books should -be our guides, but not our infallible precepts. Professor Floury considers that nearly all quartz in Nature

■ owes its existence to the decomposition of sulphide of silicium by water, and points out his reason for doing so ; and ' he further states that experiments which he has made have led him to believe that gold exists in Nature in two distinct allotropic conditions — in a metallic, molecular, crystalline state, withstanding the action of oxydising agents under ordinary conditions, and in an amorphous, not metallic and oxydisable form. Plumbago and lamnblack may illustrate this idea, The former, like metallic gold, is heavy, a good conductor of electricity, and has all the appearance of a metal,; while the latter, the lampblack, is easily oxydised, is light is a non-conductor of electricity, and is amorphous- That in sulphurets' the gold is mo stly present in both modifications, and niay sometimes be found in a chemically combined state. ____________