Gemstone -
Black Star Sapphire
Black Star Sapphire is an exotic cousin of the gemstone sapphire usually thought of as blue. Sapphire is a type of corundum that comes in a wide range of colors, including yellow, pink, purple, blue, and green and even a color-changing variety. When corundum comes in red it is called ruby, and when pinkish-orange it is labeled padparadscha. The black color of the Black Star Sapphire comes from the presence of vanadium, iron impurities, or titanium inclusions. This gemstone is set apart from the more ordinary variety by a spectacular display of a soft white, six-pointed star from the center. This phenomenon is created by mineral inclusions called rutile, sometimes also referred to as silk which, unlike most blemishes found on gemstones, actually adds a lovely uniqueness to the stone.

Stars may appear as a faint wink of white across the stone’s surface or more pronounced with milky white spikes of the star’s prongs. Rarer than a six-pointed Black Star Sapphire is the 12-pointed star. These star rays can be enhanced and even drawn out of sapphires by a process of heat treating called diffusion. Some white starred black stones are erroneously called Black Star Sapphire, but are actually the less valuable star diopside, which has only four rays to the star. Stars are best viewed in bright sunlight or with an incandescent bulb.

These rays of brilliance are found on clear to nearly opaque dark brown-black to black sapphires and are almost always found on oval cut cabochons. Their exclusive showiness is most often the focal point when set in rings, earrings, and pendants. Black Star Sapphire cut into faceted designs will lose the star, providing a challenge to gemstone cutters for maximum showpiece value. Quality Black Star Sapphires are rare, and the finest are from Chanthaburi, Thailand, known for their clear black sapphires with golden stars. Although sapphire is a very hard gemstone and can tolerate heating to bring out star qualities in a Black Star Sapphire, care should be taken when leaving this or any gemstone in direct sunlight for long periods of time.    
Compound : Aluminum Oxide
Mohs Scale(Hardness) : 9
Found : Africa, Australia, Burma, India, Sri Lanka, Thailand, and United States