Star Ruby
A Star Ruby is a rare and valuable variety of ruby that exhibits a unique optical phenomenon known as asterism. Asterism is the appearance of a star-like pattern on the surface of a gemstone when it is illuminated by a direct light source. In the case of Star Rubies, this star-like pattern typically consists of intersecting lines that form a visible star shape.
The star effect in Star Rubies is caused by the presence of needle-like inclusions of a mineral called rutile within the ruby crystal. These inclusions align themselves in such a way that they reflect light in a specific manner, creating the star pattern. The most common Star Rubies display a six-rayed star, but variations with four or twelve rays can also be found.