This is especially true of blue sapphires because they are found in so many locations and have sometimes been considered the most beautiful of the blue gemstones. Thanks to this deep history, coupled with the fact that they occur in a whole rainbow of colors, rich cultural symbolism surrounding this special stone has developed in many cultures. Sapphires have captivated the imaginations of people for thousands of years. Star sapphires (as these gems are commonly referred to) are usually cut into a smooth, domed cabochon to highlight the star effect. Rutile can align so that a four, six, or twelve-rayed star appears in the stone.

Also, corundum is one of the few gemstone species which may display 'asterism', a phenomenon caused by rutile inclusions, rather than trace elements, within the crystal.

These gems alternate between cool blues and violets in daylight, to a warm reddish-purple in incandescent light. Sapphires with the element vanadium in their crystal lattice display a color change effect under different lighting conditions. Finally, there are rare varieties of corundum that have what are called 'phenomenal' effects.

September sapphire