Mr Montgomery's Lecture.

Thames Star, Volume XVII, Issue 5272, 10 December 1885, Page 2

Mr Montgomery's Lecture.

The lecture last evening was given by Mr Montgomery to a very fair audience Mr D. E. O'Sulliuan occupying the chair. The subject was Ore Dressing, and in starting he said he would describe the various processes of separating the valu able minerals from the vein stone which is sometimes useful when it comprises fluorite and non metallic baryte, or zinc blende, manganese, spar &c , but is. often found to interfere greatly with the reduction of minerals. Among the commonest vein stones are quartz, gypsum, feltspar ; the specific gravity of which are from 2 to 3. From 3to 4 there are others such as fluorspar, malachite, zinc blende, and, carbonate of iron. From 4t05 is a long list of valuable minerals, magnetic pyrites, salts of pyrites, titanic iron sand, magnetic iron and heavy spar. From 5 to 6, sulphides of capper, silver, and lead, ruby silver, and other silver ores, oxide of copper. The most valuable silver ores are from 6 to 7 specific gravity, also black oxide of copper and antimony. From 7 to 8, sulphide of silver, galena &c. There arc not many heavier than 8, except, gold, silver, mercury,( bismuth, platinum, and cinnabar, the latter being 9 times as heavy as water. All the more valuable minerals are 3 or 4 times as heavy as the veinstone, none of them less than twice as heavy. In treating these when ground, we have these specific gravities, which are known, to go upon. In order to take the fullest benefit of these, the ore must be crushed, and then classified m particles of the same size, ihis being a point often over looked, but of great importance, and then they must be divided according to specific weight. The ore, after being broken, is dressed dry, then usually thrown on screens, so as to have the different sizes classified, and the larger pieces are again broken up. In large German establish* meats the broken ore is put on gratings over which jets of water play. Boys pick out the ores and throw into bins, separating, the ziuc and the galena. By this picking a large quantity of pure ore is got, ready for treatment; the|seconds or next quality, and the thirds or last quality being thrown into separate bins. The next process is crushing. The fineness of crushing depends on the character of the ore ; gold is crushed fine, but other .ores, such as galena or copper, are not so necessary to bo crushed fine. Crushing is done in stages, the coarse ores Jby them selves, and never mixing the fine and coarse together, and when crushed to a certain fineness they are passed through sieves. Mr Montgomery next desoribed the Cornish roller, which caa crush a large quantity, in which the stuff falls on inclined sieves placed under the roller, with an endways motion. Then the ordinary stone-breaker, so well known as not to require any description. The best way of using it is as at Freiburg in Saxony, where they use two stonebreakers, one of these breaking the stone to about half-an-inch diameter, and the other grinding it finer Neither the roller nor the stone-breaker do well for gold or silver ore, for which a stamper battery is the more suitable. Two new machines somewhat on this principle have been lately invented called the Dingley and the Heberle mills, and these are coming into notice. The great advantage of both these mills is that there is no fine slime at all, and that they do I not crush the ore so fine that the particles I float and cannot be saved. The maker of the Heberle Mill claims that it will crush nearly double as much with the same power as a stamping plant, with half as much water. Another machine for dressing ores is the Disintegrator, which, however, is quite unsuitable, owing to the large quantity of slime produced, bo that it is not possible to save the gold by any gold saving appliances we have. The next machine described was the Krom' Rolls, which have been lately mtroducedinto Nevada, and found suitable A Mr Stetefeldt, a great American mining expert, speaking of these machines, mentions an improved process of lixiviation, and entering as we are now doing in this district, on a new industry, it is a matter of great moment to us to get the newest and best improvements in machinery and processes. Mr Stetefeldt speaks very highly of this invention. The remainder of the lecture was given to describing various kinds of Jigging machines, such as hand jiggers, mechanical jiggers, hydraulic jiggers, continuous or self* acting, &o. These are for sorting and classifying the stuff after it has been crushed. In conclusion he said that he would finish this lecture this evening on the treatment of fine grained ore and slimes.