Show S IV IV Z 0 IV 1 IV 0 t S 2 10 1 40 0 1 11 1 10 A 5 t f X B R M M lecture iff nt on M 1 ore te re l dressing Brez zing 7 Y A 2 f t j s v z 1 TT N interesting interest inar inz lecture entitled A dis R r ser tation on ore dressing was dej Y livered lately by mr J M callow consulting engineer of this city to the students of the university of utah at the assay office of crismon bros where mr callow has his testing plant besides the students in attendance there were professors kingsbury mccoy and lyman and wall riter ellis and others after an ins inspection lection of the testing plant which consists of a jig wilfley table hydraulic s sizer i z e r and slime classifier the two latt erthe invention of mr callow and var ious other apparatus necessary for the most complete concentration test a cut of which accompanies this article the lecturer proceeded with his text af after ter describing the object of ore dressin dressing 01 and giving instances from practice of its com mercial value and importance an exhaustive description of the various machinery employed followed the subject being dealt with from both a theoretical and practical standpoint the lecture was copiously illustrated with drawings diagrams and samples mr callow said in part that in the employment of any milling process for the extraction of the precious and their associated metals from their ores the crushing of the ore was not only the operation first in order but in the majority of cases the first in relative importance primarily by reason of the large lare proportionate expense of the operation and secondly since it was strictly a preparation of the raw material for processes to follow the final result of the whole combination would in a great reat measure depend upon the CALLOWS concentration TESTING PLANT degree of precision attained in carrying out this preparatory treatment rolls were single function machines performing the single operation of crushing the screening of their product being effected by extraneous apparatus which being independent of any restriction imposed upon it by boina being made a part of the machine admit of exact proportioning of it to the quantity and quality of the work to be done and in a definite way returning to the machine only those particles actually needing further reduction stamps and mills were double function machines in that they effect the double duty of both crushing crushia 1 and screening their finished product the objection to them being beina 1 their W t 0 4 2 4 JW tendency to produce slimes owing more to their restricted and inefficient screen area than to the particular application of the mechanical forces emo employed loved whatever process was to follow the first object should be to avoid as far as possible the making of slime first by reason of the large percentage of loss and the mechanical difficulties unavoidable in the treatment of the slimy portions and that when the mineral portions are crush crushed ed fine they yield far more very fine slimes of value than the average of the ore so that the greater amount of mineral that can be recovered coarse the less will the final losses be secondly the extravagant waste of power owing to the needless com of a large 0 proportion of the material in many cases it is possible by a judicious arrangement of machinery to gradually reduce the ore so as to effect a saving ing of from 25 per cent to 50 per cent in power over the old prevailing methods of pounding it to smithereens accompanied by an almost corresponding increase in the percentage of values recovered separating or finishing machines included screens hydraulic jigs tables and bubbles in the whole practice of ore dressing there was no one more important point than that of sizing the material whether for jigs or tables for by its means not only is each machine capable of greater tonnage but also of doing closer work this was illustrated not only from a theoretical analysis of the subject but also by numerous examples from practice common sense alone would indicate that a machine adjusted with stroke speed and water for treating half inch material cannot be expected to do good work on particles of one hundredths of an inch nor can tables adjusted for slopes and water to treat 20 mesh sizes be expected to extract and save with the same precision grains one five hundredths of an inch in diameter ores may be similar but it is rare indeed to find two ores that are identically aeike alike and as the treatment must be suited to the ore the several methods and their variations for treating I 1 them are almost as diverse ores were spoken of as either smelting smelling sm elting chlorinating chlorina ting cyaniding cyan iding amalgamating ga or concentrating to determine which and to design the most suitable plant being beina the work of the metallurgist an eye inspection might be all that was necessary to decide which would be the most suitable process for an ore but before the plant can be intelligently designed in all its parts its individual properties and peculiarities must be studied and thoroughly understood A disregard for this precaution had left in nearly every mining camp a ment of so folly in the shape of some idle or ruined reduction works or the rusty and decaying machinery of some disemboweled disembowel ed mill A mistaken idea prevailed that the suitable process could only be determined by a large scale test at some mill the nearest one might be wholly unsuited to the ore and large quantities might therefore have to be sent long distances the results were invariably disappointing the actual information obtained being out of all proportion to the expense and time involved such tests might be valuable in demonstrating to the uninitiated the might be expected on a working scale but for supplying actual data for the skilful design of a successful plant they were uniformly inferior to a properly conducted laboratory test it would however be admitted by even those who might differ with this view that the laboratory tests should in every case precede a mill run so that guided by the information obtained in the laboratory a really suitable plant could be selected and a full scale run made with profit and to good purpose A laboratory concentration test is to all intent and purposes a mechanical analysis and nd is to the metallurgical engineer what a chemical analysis is to a smelter man the sample to be worked upon might be from 50 to lbs ibs but must be an accurate representative of the ore bo diesto be treated both for values and physical composition too much care could not be exercised in taking this sample if the results of the test were not to be misleading the most lucid way of illustrating a test was by means of diagrams they needed no verbal explanation as from a careful study of them every operation that the ore went through is carefully portrayed with values and weights given by determining the weights at every point during the test the designer is enabled to see at a glance the which he has to deal with in the actual mill instead of having to guess at them |