Volatility of Metallic Chlorides
In Table I are cited data on the vapor pressures of the common metallic chlorides. The temperatures given are in the region of magmatic temperatures, except where a high vapor pressure is developed at a much lower temperature. Because of the volatility of chlorides, and because direct observation of volcanic sublimates shows their presence, it […]
Jigging
The jig, in one form or another, continues to hold a leading place among the machines designed to separate two or more minerals of different specific gravities. It is simple in construction, easily operated, capable of treating large quantities in a short time, and highly efficient under various conditions. The question, whether the material to […]
Economic Geology
Understanding the feed to processing operations is key to maximizing cash flow (economic value). Unfortunately the subject of economic geology is not covered within most undergraduate programs preparing students who enter the mining industry as process engineers. The good news is that there are reference materials available to help people learn these subjects. Some good […]
Overpoling Electrolytic Copper
The current meaning of the term, copper overpoled in the reverberatory furnace, is that poling has been carried beyond the tough-pitch stage, with the result that the reduction has been carried too far, causing the copper to become porous and brittle, and thus unfit for industrial purposes. It will be shown that the brittleness of […]
Hydraulic Jig Concentrator VS Shaking Table
Concentration of grains from 10 to 30 mm. is effected by hydraulic jigs with two compartments, and in the case of the smaller grains down to 2 mm. by jigs with five compartments. The construction of the jigs is the same in both cases. Fig. 3 gives the details of a jig with two compartments; it […]
Difference between Crushing and Grinding
When making comparisons of the efficiencies of different grinding and crushing machines it is desirable to be able to estimate the work actually done in crushing the ore from a given size of feed to a given size of product, the screen analysis of both feed and product being determined. Messrs. Klug and Taylor, in […]
Underground Gold Mine Development – Sampling
This paper is intended, in the light of recent investigations, to call attention to some of the essential features of good practice in sampling and mine-valuation. Mine sampling may be divided broadly into two classes: development-sampling and computation of ore-reserves; and, stope-sampling and estimation of stope-values. Development Sampling It is with development-sampling only that this […]
Assaying Gold & Silver from Copper Alloys
The so-called “combination method” is generally used in assaying bar copper for silver. It has been modified from time to time. Briefly outlined as now practiced, it is as follows: One A. T. of the borings is dissolved in dilute nitric acid. When solution is complete the liquid is boiled and then filtered to remove […]
How to Assay and Evaluate a Gold Bar
The Bureau of the Mint of the United States Treasury maintains offices for the purchase of gold-bullion, and this paper describes an investigation to establish the reasonable differences in the assay-results at the various institutions which may be commercially allowable in the settlements between them. Beginning with the comparative assay of proof-gold at the Philadelphia […]
Adjustable Thermo-Electric Pyrometer
Frequently in using a thermo-electric pyrometer for measuring the temperature of a furnace, a hole is drilled at the back or side of the furnace, through which is introduced the tube containing the thermocouple. At times the couple is left almost where it drops, for the reason that it soon becomes too hot to be […]