Sphalerite (zinc sulfide) is a common mineral, the principle ore of Zinc, and occurs in many distinct colors and forms, making it an important mineral to collectors. Its colors are red, brown, black, green, yellow and rarely colorless. The transparent to translucent red variety is often referred to as Ruby Jack. Some transparent varieties have a dispersion (fire) that is about four times that of a Diamond. Add to that adamantine luster and spectacular colors, and it is one of the most beautiful of all cut gems. Alas, because of its softness (3.5 – 4) it is not suitable for jewelry, so it is relegated to ornamental purposes and gem collectors. This colorful mineral is associated with numerous aesthetic minerals, including Quartz, Calcite, Pyrite, Fluorite, Dolomite and Barite.