Sapphire

Sapphire gemstone, same as Ruby comes from the same mineral family, corundum. Sapphire instead of rubies can be colorless, blue, pink, yellow, orange, green, grey, black and almost any color of the rainbow. Like Ruby it is the second hardest precious stone after diamond, rating 9 on the Mohs scale of mineral hardness.
Usually corundum is opaque and only when it has good quality and color and a clean transparent clarity in its crystallization form is faceted and polished to become an awesome gemstone. Sometimes like Ruby, also Sapphire is treated by heat to improve color and clarity, some more invasive treatment which permit to use them in jewelry is diffusion with fracture filling to enhance the appearance and attractiveness of some corundum stones. Finest quality of this material comes from countries like: Kashmir in India, Myanmar, Sri Lanka (Ceylon), Thailand, Vietnam, Africa, these are the major source of the most beautiful variety of this stone.
Sapphire can occur transparent to opaque. Material with transparent clarity are the most valuable, especially in larger size with strong color saturation. Sometimes the internal inclusions can generate the asterism optical effect like for ruby. Read more.