Some gemstones (diamonds, coloured stones or assembled gems) found in the jewellery commerce, when observed by an optical microscopy or even at naked eye, exhibit unusual characteristics, such as inclusions incorporated at different depths. The investigation by confocal Raman micro-spectroscopy allowed identification of a blue sapphire and of nanocrystalline anatase in the same surface region of a cut and polished diamond. Moreover, hematite (α-Fe2O3) inclusions of rectangular shape, embedded at different depths, ranging from a few microns to some tens of microns beneath the gemstone surface, were identified in the coloured stones. Finally, a detailed study of an assembled gem evidenced spectral features that can be put in relation with its fabrication process. Copyright © 2012 John Wiley & Sons, Ltd.