Natural Sphalerite 5.00 caratSphalerite Gemstone natural sphalerite gemstone. Sphalerite is a mineral that can come in various shapes and colors, often used in jewelry when cut and polished. An 5. 0 carat octagon shaped sphalerite would likely make for a stunning and unique piece. Natural sphalerite, with its captivating luster and rich colors, is a gemstone prized by collectors and enthusiasts alike. Formed from zinc and often found alongside other minerals, sphalerite showcases