multicolourgems:The red variety of the corundum family, ruby has been the world’s most valued gemsto
multicolourgems:The red variety of the corundum family, ruby has been the world’s most valued gemstone for thousands of years and star rubies arguably the most stunning gems, featuring an illuminated star just bellow the surface when cut en cabochon. The star effect is caused due to an optical phenomenon known as “Asterism”, when light reflects from needle-like inclusions of rutile aligned perpendicular to the rays of the star. -- source link