2026

Rare encounter: Sapphire with grandidierite needle inclusion

By Dr. Michael S. Krzemnicki, first published in Facette 30 (March 2026)
Recently, the SSEF received for testing a sapphire of pale blue colour with a distinct colourless needle-like inclusion, resembling to some extent long prismatic pargasite needles known in Kashmir sapphires (Figure 1).
Figure 1: Pale blue Sri Lankan sapphire with colourless needles of grandidierite as inclusion. Microphoto: M.S. Krzemnicki, SSEF.

When analysing this inclusion with Raman microspectroscopy (Figure 2), we were more than astonished to find out that the inclusion is grandidierite, a magnesium aluminium borosilicate with the ideal chemical formula (Mg,Fe2+)(Al,Fe3+)3(SiO4)(BO3)O2. It was first discovered in 1902 by Alfred Lacroix in southern Madagascar and named in honour of Alfred Grandidier (1836-1912), a French explorer and scholar who studied extensively the natural history of Madagascar.

Figure 2: Raman spectra of a faceted grandidierite compared with the colourless grandidierite as inclusion in the descried sapphire (the peaks with * are due to the sapphire). Figure: M.S. Krzemnicki, SSEF.

Gem-quality grandidierite is a very rare collectors’ stone (see SSEF Facette 2018 and 2020) and usually exhibits bluish green to greenish blue colour of various saturation in relation to its iron concentration. In cases which present very low iron concentrations or the absence of iron, the mineral is colourless as in case of the needle-like inclusions in this sapphire.

In literature, only two similar cases of needle-like grandidierite inclusions in sapphire have been reported (Hain & Hughes, 2019). Certainly, because this mineral inclusion is very rare, but probably also because these colourless needles may be misinterpreted (e.g. as pargasite) and their true nature ‘overlooked’ in sapphire testing. Based on our testing and data, this sapphire originated from Sri Lanka (a known source locality of grandidierite), Kashmir as an origin of the sapphire could be definitively excluded.