Lot Natural Grandidierite Rough Crystals 57.5ct

The largest of the three rough grandidierite parcels at 57.5ct, roughly two dozen fragments in pale to medium aqua and blue-green. What stands out here is the banding: many of the pieces show a clear aqua zone sitting directly against white or silvery matrix, so the boundary between gem material and host rock is visible on a single fragment rather than only across the parcel. Surfaces are mostly frosted with occasional glassy fracture faces, one piece carries a strong rust-orange cap of iron staining, and a handful run greyer and browner than the rest. The overall tone sits between the deep teal lot and the palest one.

Grandidierite forms in aluminium-rich metamorphic and pegmatitic rocks, and parcels like this one show that relationship plainly, with the colored mineral still locked against the pale material it grew in. Untreated. At 7 to 7.5 on the Mohs scale the pieces are hard enough to work, and the banded fragments in particular can be cut so the contrast between aqua and white matrix is kept rather than removed. Individual pieces run roughly 8 to 14mm, sold as the complete parcel.

Natural grandidierite rough, Madagascar, sold as a complete lot.