Assaying is the chemical analysis of a material, or object, for one specific metal or chemical element of particular interest. It separates precious metals from a known amount of sample. This International Standard specifies a cupellation method (fire assay) for the determination of gold in gold jewellery alloys. The gold content of the alloys should preferably lie between 333 and 999 parts per thousand (‰). The procedure is applicable specifically to gold alloys incorporating silver, copper and zinc. Some modifications are indicated where nickel and/or palladium are present in the so-called white gold alloys, as well as for alloys containing 990 or more parts per thousand (‰) of gold. This method is intended to be used as the reference method for the determination of fineness in alloys covered by ISO 9202.
Silver Assaying (Potentionmetry Method)
Silver is one of the one of the most famous ornamental metal and due to its intrinsic beauty it is made into rings, bracelets, ear-rings and other jewellery items, ornamental utensils, cutlery, tray dishes and coins. Silver's weakest point is its notorious tarnishing habit. Fresh silver has a bright metallic white color but almost invariably turns yellowish to blackish upon expose to air which is due to its chemical reaction with Sulphur present in Hydrogen Sulphide found in small quantities in the atmosphere. It is not affected by Oxygen or Water.
XRF is a proven technique for material analysis in a broad range of industries and applications; from Positive Material Identification, scrap metal sorting, measuring sulfur in oil, analysing coating thickness of metal finishing and metal alloys to quality control in the electronics and consumer goods industry.
Identifying and authenticating antique and period jewelry is based on experience and knowledge. It is often a process of comparing known with unknown and making an educated guess. But those of us who search for clues to a piece's age and origin are always delighted to find a hallmark on a jewel, because it eliminates a great deal of guesswork. Learning how to identify hallmarks is an essential part of becoming an expert in the field.