Semi-precious stones, as well as rocks belong to the mineral world. Again, the role of CARAA is to determine the most efficient methods to scan an object according to its value, size, conservation state and, the sampling opportunities … or the non-invasive possibilities.
• Choosing the appropriate techniques
Understanding a gem or a mineral might be complex. It is indeed rare that a single technique allows to identify all the problems related to a mineral. For example: what is the cause of the yellow colour in a diamond? is it natural or due to irradiation or heating induced by man? What kind of inclusions does it contain?
• A role of expertise at CARAA
Confirming or infirming the composition of a rock or a crystal consist in authenticating it. Some common examples are the differentiation between diamond and its substitutes (zircon -ZrO2- or moissanite -SiC-), an amethyst from a coloured glass or, a crystal rock (quartz) from a glass (see the image of the Aztec crystal rock skull below).
• Identifying sources and provenance
The geographical source of a gemstone or a mineral can be determined by analyzing the natural inclusions embedded in it during its geological formation. The geographical location of many types of marble is another example of potential source analysis.