Retorting Amalgam & Melting Bullion
It sometimes falls to the lot of the assayer doing commercial work or working in a mining camp to retort the amalgam taken from the plates of a stamp mill and melt the resultant sponge of gold and silver into a bar, and assay the bar so the value of the product may be known. […]
Distilled Water for Assay Laboratory
Why Distilled Water In all operations in assaying and chemical analysis it is desirable to use distilled water. There are very few places where the assayer cannot procure distilled water. How to Purify Water for Laboratory Purposes without Distilling If it is necessary to use ordinary water, add a few drops of nitrate of silver […]
Volumetric Assay Copper Determination by Solution of Potassium Cyanide
The general method of assaying copper values is by what is termed the “wet” process, that is volumetric determination by titrating with standard solution of potassium cyanide. This method is very accurate when carefully done, but care must be taken to keep the standard solution at a given strength. Preparation of Sample The original sample […]
Gold Purity Testing
Description of Touch Stone and Test Needles The touch or test stone is practically a small black whetstone. Test needles (Fig. 47) are a number of slim pointed brass fingers, one end having gold points of different fineness expressed in karats (the karat is the jeweler’s standard of measure for gold, and 24 karats is […]
Smelting Fluxes
General Flux In a laboratory where much work is done in a day, and the class of ore is uniform, what is called a “general smelting flux” may be made. This flux is adapted to ores that may be classified as average, but is so compounded as to allow the addition of extra litharge and […]
Assay Balance Scale for Weighing Samples
Analytical Balances Buy a good button balance, for should the final weighing of the gold or silver recovered from an assay charge be inaccurate, all the previous work will have been wasted. A good button balance can be purchased for $100.00 (Fig. 42); higher grades that are more sensitive and delicate of construction will cost […]
Fire Assay of Antimony
Usual Charge Mix 10 grams of the pulped ore with 40 grams of pulverized potassium cyanide. Melting Put the charge into a 20 gram crucible or one of equivalent capacity, and cover the top of the charge with about 10 grams of dry table salt. The salt cover prevents the charge from boiling over the […]
Gold Bullion Assay
Drilling Bullion Bar for Sampling Bullion submitted for assay is usually brought in the form of bars, bricks, slugs or buttons, and a sample of bullion in this form is best obtained by drilling into the brick or slug with a small bit 3/16″ in diameter (Fig. 32). Drill enough so that the shavings or […]
Scorification
Definition of Term Scorification: Scorification may be defined as a reduction and a partial or preliminary cupellation successively performed in the same container without removal of the container from the muffle until volatilization is stopped by the slag entirely covering the charge. When is Scorification Assay Used Scorification is the proper method of assaying copper mattes. […]
How to Assay Gold & Silver Ore
Classification of Ores In fluxing ore for gold and silver, first determine the nature of the sample submitted for assay. Three different classifications may be made in the preliminary examination of ores; first, pure quartz (very glassy or vitreous); second, no quartz (plastic and free from grit); third, a mixture of these two extremes which […]