One copper electroformed Hand Knapped Obsidian Heart complete on a 20" soldered copper chain. Obsidian is an igneous rock occurring as a natural glass formed by the rapid cooling of viscous lava from volcanoes. Obsidian was used by early Native Americans and many other primitive peoples for weapons, tools, and ornaments. Ancient Aztec and Greek civilizations used the material for mirrors. Hearts measure approximately 1.75" x 1.5". Size, shape, and color may vary as no two glass pieces are alike.