An “asterism” is an optical phenomenon occurred in typically corundum and other gems. When the stone is cut as a dome cabochon, a four to six rayed figure is displayed on the dome. Star stones get their asterism from the titanium dioxide inclusions of tiny fibers of rutile or silk. The stars are caused by the light reflecting from needle-like inclusions of rutile aligned perpendicular to the rays of the star. 

When mentioned about sapphire, blue is the all-time favourite color and the most classic choice. As color is the most important determinant, saturated hues that are neither too light nor too dark being the most valuable.

Royal Blue Sapphire is medium dark blue color in tone. Gems that have little or no gray or brown modifier are described as vivid. Royal Blue Sapphire with vivid saturation considered most valuable. Royal Blue Sapphire from Sri Lanka still considered most valuable compared to royal blue sapphire from rest of the world. 

Sapphire over 2 carats are rare and prices tend to increase exponentially with carat weight. Any high quality blue sapphire over 5 carats would be regarded as very rare and collectible.

​White sapphire and diamond may seem identical. Both give off a bright white glow, and even come in similar forms. Still both types of materials exhibit many unique characteristics and benefits. These factors are color, light refraction, durability and price. White sapphire is genuine sapphire that is colorless and has the same hardness as sapphires in other colors. Diamonds refract larger amounts of light, and therefore shine brighter. White sapphires have good durability and come second only to diamonds when you compare hardness on the Moh's scale of hardness. Price of white sapphires which is much less as compared to diamonds.