Ruby is the most expensive among all corundum gems because it contains chromium (CR, โครเมียม), because the output of ruby is very small. Compared with sapphire, the output is only 1/5 of that of sapphire; and ruby is usually very crystallized. There are not many rubies larger than 5 กะรัต. Rubies larger than 10 กะรัต […]
