Ruby zoisite is a natural combination of green zoisite and ruby, often containing black hornblende or other dark minerals. The green zoisite forms through metamorphism of calcium- and aluminum-rich rocks, while ruby—red corundum colored primarily by chromium—develops within the same geological environment. The contrasting green, red, and black colors give the stone its distinctive appearance. Major sources include Tanzania, especially the Longido and Merelani regions, with additional material reported from Kenya, Norway, India, and other metamorphic-rock localities.

Under ultraviolet light, the ruby portions may fluoresce a bright red to pinkish-red, particularly under long-wave UV, because chromium can activate ruby’s fluorescence. The zoisite matrix is generally nonfluorescent or only weakly reactive, so the response can appear patchy and limited to the ruby crystals; some specimens may show little visible reaction depending on chromium concentration, surface polish, lighting, and matrix composition. 

Ruby zoisite is commonly associated in metaphysical traditions with vitality, emotional balance, passion, growth, and the integration of grounded energy with heart-centered awareness. These properties are spiritual beliefs and have not been scientifically proven.