Grandidierite

Carat weight is a major driver because transparent grandidierite suitable for faceting is scarce and usually small. Fine-quality stones above 1–2 carats are rare, and gems above 5 carats of high quality are exceptional and can command very high per-carat prices.

Color is critical. The most valuable grandidierite displays a vivid, medium to medium-dark bluish-green with good saturation and minimal gray. Too dark stones can appear inky, while overly light or grayish material is less prized. Pleochroism must be managed through orientation to present the best hue face-up.

Most grandidierite is included or translucent; thus, any stone with high transparency and only minor inclusions is rare and valuable. Eye-clean or nearly eye-clean stones in attractive color are extraordinarily scarce. Heavily included or opaque material is typically cut into cabochons or sold as specimens at lower prices.

Cutting grandidierite is technically demanding due to its pleochroism and scarcity. Cutters orient stones to maximize the most pleasing bluish-green direction while balancing brightness and tone. Well-proportioned, symmetrical cuts with good polish are highly valued, particularly when they successfully showcase both color and brilliance.

Grandidierite was first discovered in Madagascar, which remains the principal source of gem-quality material, with minor occurrences reported elsewhere. Even in Madagascar, transparent, facetable rough is extremely limited, and much of the output is translucent or opaque.

Demand is driven almost entirely by high-end collectors, connoisseurs and specialty colored-stone dealers. As awareness of the gem's rarity and beauty has grown, competition for fine stones has intensified, supporting strong price levels.

Recent Trends: niche but stable collector interest, with fine, well-documented stones achieving strong prices through specialist dealers and auctions.