This is a large, exceptionally well crystallized, and very important example of this extremely rare species. The mineral gets its name from Serendib, the old Arabic name for Sri Lanka. Serendibite is a very rare, seldom crystallized member of the Sapphirine Supergroup of minerals. This particular crystal is very well formed and well terminated with very sharply formed crystal faces and edges. This fine crystal also exhibits rarely seen polysynthetic twinning parallel to its tabular dimension! Serendibite is a rare complex calcium-magnesium-aluminum borosilicate mineral and is very rare in good crystals like this! This rarity has a mass of 6.19 grams. Interestingly, some crystals have been sold as gem rough (they are faintly translucent when cut) for the collectors of rare gemstones. This is an important, competitive-level thumbnail specimen from very old finds.