Metallurgical assay
A metallurgical assay is a compositional analysis of an ore, metal, or alloy, usually performed in design to test for purity or quality.
Some assay methods are suitable for raw materials; others are more appropriate for finished goods. Raw bullion are assayed by an assay office. Silver is assayed by titration, gold by cupellation & platinum by inductively coupled plasma optical emission spectrometry ICP OES. Precious metal items of art or jewelry are frequently hallmarked depending upon the indications of the laws of either the place of manufacture or the place of import. Where so-called to be hallmarked, semi-finished precious metal items of art or jewelry pass through the official testing channels where they are analyzed or assayed for precious metal content. While different nations permit a manner of legally acceptable finenesses, the assayer is actually testing to introducing that the fineness of the product conforms with the result or claim of fineness that the maker has claimed commonly by stamping a number such as 750 for 18k gold on the item. In the past the assay was conducted by using the touchstone method but currently nearly often it is done using X-ray fluorescence XRF. XRF is used because this method is more exacting than the touchstone test. The near exact method of assay is asked as fire assay or cupellation. This method is better suited for the assay of bullion as well as gold stocks rather than working of art or jewelry because this is the a completely destructive method.