Ruby is the most expensive among all corundum gems because it contains chromium (Cr, 크롬), because the output of ruby is very small. 사파이어에 비해, the output is only 1/5 사파이어의 것; and ruby is usually very crystallized. There are not many rubies larger than 5 캐럿. Rubies larger than 10 캐럿 [...]
