A mineral is usually described by a chemical formula that indicates the type and amount of its major chemical elements. The chemical formula is a simplified representation of the composition of the stone and usually contains the main elements only. However, there are other chemical compounds present in a stone in smaller quantities: these are the trace elements. In gems, trace elements are often the agents responsible for adding colour. Despite their small contribution to the overall chemical composition of the gemstone, trace elements play a key role in determining whether a mineral is just a standard stone or a rare and coveted gemstone. By means of chemical analysis, gem labs can identify and quantify the presence of such trace elements, which also give valuable hints as to the geographic origin of a gem.
Aside from the main and trace elements, gemstones also contain a very high number of other elements in minute concentrations of a few parts per million or billion. These so-called ultra-trace elements typically do not have any significant influence on the appearance of the gemstone, but they shed light on the environment in which it grew thousands, millions or even billions of years ago. The type and amount of these elements in a gemstone are often indicative of a specific location and are used by gem labs to determine its country of origin.
