Ruby Zoisite occurs naturally when small Ruby crystals become embedded within Zoisite. The Ruby inclusions in this stone are pink to reddish purple to dark purple, while the Zoisite is light to medium green. Ruby has long been considered one of the most beautiful and valuable gemstones on the planet. It is also one of the hardest, second only to Diamond. At times in ancient history, Ruby was valued more highly than any other gem, including Diamond. It’s believed that Kublai Khan once offered an entire city in trade for a sizable Ruby.