Natural Grandidierite
The Grandi
Grandidierite is a rare magnesium-aluminium borosilicate, first described from southern Madagascar and named after the French explorer Alfred Grandidier. It is one of the ten rarest gemstones on most lists, prized when transparent and free enough to facet.
The Grandi is a 17.40 ct oval, cut in a modified brilliant pattern, and documented in an independent laboratory report as natural grandidierite with no detected treatments.
Rarity Score: 9.8 / 10
Reference stones
- Grandidierite · Medici Collection LLC · 764 ct (Guinness Record)
Location: Stockholm · Private collection · JDBG GEMS
A matter of scale
Faceted grandidierite is extraordinarily rare; clean crystals large enough to cut are seldom encountered. At 17.40 ct, The Grandi is a substantial documented example of this mineral.
Why it is difficult
Grandidierite is strongly trichroic and typically heavily included. The cutter must orient the stone to show its blue-green face while working around the inclusions that make transparent rough so uncommon.
Provenance
Acquired as part of a single-lot parcel of rare collector stones; chain of custody is documented from the cutting workshop to the Institute.
Documentation
Verification is in progress. Laboratory documentation, photographic record and acquisition history are held on file and shared in full with serious enquirers.