Grandidierite

Grandidierite is an extremely rare and valuable mineral, first discovered in 1902 in Madagascar by the French explorer Alfred Grandidier, after whom it was named. It is a magnesium aluminum borosilicate (MgAl₃(BO₃)(SiO₄)O₂) and is known for its striking blue-green to deep teal color, caused by traces of iron in its crystal structure. Grandidierite is highly pleochroic, meaning it displays three different colors—blue, green, and colorless—depending on the viewing angle, adding to its visual appeal.This gemstone crystallizes in the orthorhombic system and has a hardness of 7.5 on the Mohs scale, making it durable enough for jewelry. However, gem-quality transparent grandidierite is exceptionally rare, as most specimens found are opaque or translucent. The finest facetable stones come from Madagascar, particularly from the Maromby area, which remains the primary source of high-quality material. Other small deposits have been reported in Sri Lanka, Namibia, and Malawi, but they are not commercially significant.Due to its scarcity, grandidierite is considered one of the rarest gemstones in the world, with transparent, facetable specimens fetching prices as high as $20,000 per carat. Its combination of rarity, stunning color, and unique optical properties has made it highly desirable among collectors and gem enthusiasts. Despite its durability, grandidierite is rarely used in mainstream jewelry, as the supply remains extremely limited. As new sources are explored, it continues to be one of the most exclusive and sought-after gemstones globally.