The dating of a rock is possible, but it indicates the formation of the material and not the timing of phase sculpture, which is more our problems.
The analyse of the material and its alteration by scanning electron microcopy (SEM ) provides a body of evidence to decide on the antiquity of the sculpture.
Degradation of the stone is relatively slow; these studies will be performing for objects at least 300 years old.
At least one sample of a few millimeters is necessary for this analysis.
Depending on the nature of the rock (sandstone, limestone, marble, slate, jade ...), the corrosion process is more or less strongly developed. Nevertheless, for ancient sculptures, we should observe a gradient between the carved surface and the heart of the material.
The inner zone of the rock is by definition better preserved. Consequently, it should have a different texture than the carved surface. This corresponds to the gradient of alteration between the surface and the interior of the material, we seek to highlight. This result indicate that the stone is naturally long and altered.
In the opposite case, the absence of this gradient reveal that the object is modern. Know more
Dr Stéphanie CASTANDET
intervenant en étude optique préliminaire
We can also carry out a study to identify surface traces of shaping, polishing, chip tools, superrficial deposits ...
This step reveals information, but it is by no means sufficient to establish the age of an object.
Rock cristal test, a CIRAM exclusivity
The rock crystal (quartz) is a very durable material and does not alterate. The methodology presented above can not then apply.
Nevertheless, we propose an alternative technique based on the gradual penetration of the water in the crystal.
The depth of penetration of the hydrogen atoms will be an indicator of antiquity.
More hydrogen will be detected deeper, more the object would be anceint.