Tsavorite is one of the gem varieties of the garnet mineral called grossular. The more common gem variety of grossular is called hessonite. Gem quality tsavorite is found at Tsavo, Kenya. The green color is caused by trace amounts of vanadium. Tsavorite is not the only green garnet. While Uvarovite is almost never used as a gemstone (the crystals tend to be tiny), the green andradite garnet variety called demantoid is sometimes cut for gems. Distinguishing them can be difficult, but experienced gem dealers are capable of doing so.