Assaying

The most promising core and hand samples invariably wind up in a laboratory to be analyzed. Assaying is the process in which the precise constituents of the rock are to be measured and catalogued.

An assay method that best determines the concentration of the metal of interest isw chosen by the chemist. The methods which are commonly used these days are:

Fire assaying, in which the sample is melted and the elements that are not wanted are chemically removed;

Wet assaying, in which one dissolves the sample and metals are recovered chemically by using reagents;

Instrumental analysis, in which the atomic properties of the metals are detected – for instance, their response to visible light or x-rays.

After the results of surface assay are returned from the laboratory, the location of the samples and the corresponding assay values of the same are plotted on a map to give a picture in two dimensions of the ore zone that has potential.

Core assays are similarly plotted on maps in later stages of exploration, this way they add a third dimension that makes it possible for the geologist to visualize the complete orebody.

When referring to the case of gold exploration, any high values that are unusual are cut; in other words, they are not included in the average. Isolated high values are found frequently not to reflect the grade around the sample locarion.

If the result of the assay is from a length of core or a channel sample, it is always written in terms of concentration of metal over a given length – as an example, 5 grams gold per tonne (0.15 oz. Per ton) over 8 metres, or 10 feet of 3% nickel. While these are only two-dimensional snapshots of a mineralized area, a sufficient amount of them in the same vicinity combine to form a three-dimensional picture of the grade and the tonnage of a deposit.