Black Tourmaline Faceted Microbead NecklaceA strand of black mineral lighteach microbead faceted so the necklace catches light despite the stone's opacity. Black Tourmaline (Schorl) is a boron silicate mineral, Mohs 77. 5. Despite being opaque rather than translucent, the facets on each microbead catch direct light and produce a subtle surface shimmerthe effect is understated but present, unlike a smooth bead which reads as pure matte black. The beads are strung collar length. Major sources