As variety of the mineral corundum, sapphires come in all colors of the rainbow with the exception of red corundum which is a ruby.
The prices of natural sapphires varies depending on their color, clarity, size, cut, and overall quality – as well as their geographic origin. Some of the most valuable colors of sapphire are a cornflower blue color, known as Kashmir sapphire or cornflower blue sapphire as well as the beautiful padparadscha sapphires; a pink-orange corundum with a distinctive salmon color. Found mostly in Sri Lanka they’re extremely rare and very expensive. Various other elements and concentrations color sapphires pink, lavender, orange, green, purple, and peach-apricot.
Over the centuries Sri Lanka consistently produced stunning varieties of pink, blue, and yellow sapphires, in addition to red, pink, and blue star corundum. Sapphires can also be found in Kashmir, Burma, Sri Lanka, Madagascar, Thailand, Cambodia, Australia, Tanzania, Kenya, and the USA.
Blue sapphires are evaluated based upon the purity of their primary hue. Purple, violet, and green are the most common secondary hues found in blue sapphires. Violet and purple can contribute to the overall beauty of the color, while green is considered to be distinctly negative. Blue sapphires with up to 15% violet or purple are generally said to be of fine quality. Blue sapphires with any amount of green as a secondary hue are not considered to be fine quality. Gray is the normal saturation modifier or mask found in blue sapphires. Gray reduces the saturation or brightness of the hue and therefore has a distinctly negative effect.
Padparadscha is a pink-orange corundum, with a low to medium saturation and light tone, originally being mined in Sri Lanka, but also found in deposits in Vietnam and Africa. Padparadscha sapphires are rare; the rarest of all is the totally natural variety, with no sign of treatment.
Fancy Color Sapphire
Yellow and green sapphires are also commonly found. Pink sapphires deepen in color as the quantity of chromium increases. The deeper the pink color the higher their monetary value as long as the color is tending towards the red of rubies. Pink sapphires are a fashion favorite.
Color Change Sapphire
A rare variety of sapphire, known as color change sapphire, exhibits different colors in different light. Color change sapphires are blue in outdoor light and purple under incandescent indoor light; they may also be pink in daylight to greenish under fluorescent light. Some stones shift color well and others only partially, in that some stones go from blue to bluish purple. While color change sapphires come from a variety of locations, the gem gravels of Tanzania is the main source.
A star sapphire is a type of sapphire that exhibits a star-like phenomenon known as asterism; red stones are known as “star rubies”. Star sapphires contain intersecting needle-like inclusions following the underlying crystal structure that cause the appearance of a six-rayed “star”-shaped pattern when viewed with a single overhead light source. The inclusion is often the mineral rutile, a mineral composed primarily of titanium dioxide.
The stones are cut en cabochon, typically with the center of the star near the top of the dome. Twelve-rayed stars are occasionally found, or parallel whisker inclusions can produce a “cat’s eye” effect. The Black Star of Queensland is believed to be the largest star sapphire that has ever been mined, and it weighs 733 carats. The Star of India (weighing 563.4 carats) is thought to be the second-largest star sapphire, and it is currently on display at the American Museum of Natural History in New York City.
The 182-carat Star of Bombay, located in the National Museum of Natural History, in Washington D.C., is an example of a blue star sapphire. The value of a star sapphire, however, depends not only on the weight of the stone but also the body color, visibility and intensity of the asterism.