Hydroxyl-Herderite is a rare calcium beryllium phosphate mineral that typically occurs in pegmatite deposits as small, unimpressive crystals. This magnificent herderite gemstone from Brazil is a major addition to the National Gem Collection for several reasons. Its large size and beautiful green color make it perhaps the largest and finest known gem hydroxyl-herderite. It is a significant upgrade in that the only faceted hydroxyl-herderite gems previously in the collection weighed 5.9 and 1.2 carats, respectively. The mineral hydroxyl-herderite was first discovered in Germany; other localities include Brazil, Russia and the United States. This gem was acquired with endowment funds from the Tiffany & Co. Foundation.