A Ruby is a variety of the mineral corundum (aluminum oxide). The color comes mainly from the chromium element. The Ruby is considered one of the four precious stones, together with the sapphire, the emerald, and the diamond. Rubies were found for centuries in Burma. They have also been found in Thailand, Sri Lanka, Madagascar, Vietnam, Nepal and Pakistan. Rubies have been found in the US states of Montana, North and South Carolina.
Zoisite is a Calcium Aluminum Silicate that belongs to the Epidote group of minerals. When it is found transparent, it is formed in to gemstones while translucent-to-opaque material is usually carved into sculptural works. The latter sometimes has Ruby Crystals which are completely opaque and unsuitable as gemstones, but are well colored and contrast strikingly against the green matrix of the Zoisite. Zoisite may be green, blue, brown, pink, yellow, gray or colorless.