These tourmaline, variety schorl, crystal twins are from Erongo Mt. in the Erongo Region of Namibia. This area contains 60 different mineral species including tourmaline. Schorl is an iron rich variety of tourmaline that contains the elements Na, Fe, Al, Si, O, B, and H. This is a cluster of interpenetrating double terminated crystals. The terminations are complex. The tourmaline is black with an adamantine luster. The largest crystal is 2 inches long ( 5 cm. ). The rear of the piece is the former crystal attachment point. The cluster measures 2 7/8 x 2 3/16 x 1 3/16 inches or 73 x 56 x 32 mm.