Sapphires and their close cousins, Rubies are members of the corundum mineral species. In gemology, a ‘species’ is a mineral that has a definite chemical formula and a specific three-dimensional structure. Corundum is an aluminum oxide (Al2O3), and has a regular crystalline structure formed by repeating patterns of arrangement at the atomic level. A “variety” is a sub-group of a mineral species and so Sapphire is a variety of Corundum just like Ruby.
While Ruby is always red, Sapphire can come in virtually every other color. Color in gemstones breaks down into three components: hue, tone and saturation. Hue is most commonly understood as the basic color of the gemstone. Saturation refers to the vividness or brightness of the hue, and tone is the lightness to darkness of the hue. Blue sapphire exists in various mixtures of its primary (blue) and secondary hues, various tonal levels (shades) and at various levels of saturation (vividness).
The color of fine Blue Sapphires may be described as a vivid medium dark violet to purplish blue where the primary blue hue is at least 85% and the secondary hue no more than 15%, without the least add mixture of a green secondary hue or a gray mask.
The most valued color is blue. 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.
Fancy Colored Sapphire (all other colors except blue)
While Blue Sapphire is the most well known variety of Sapphire, there are several other colors which are highly prized.
Padparadscha is a delicate light to medium toned pink-orange to orange-pink hue, originally found in Sri Lanka but also found in deposits in Vietnam and parts of East Africa. Padparadscha sapphires are rare; the rarest of all is the totally natural variety, with no sign of artificial treatment. The name is derived from the Sanskrit ‘padma ranga’ (padma = lotus; ranga = color), a color akin to the lotus flower.
Pink Sapphire is also highly prized. Pink sapphires deepen in color as the quantity of chromium increses. The deeper the pink color the higher their monetary value, as long as the color is tending toward the red of rubies. In the United States, a minimum color saturation must be met to be called a Ruby, otherwise the stone will be called a pink sapphire.
Yellow Sapphires in a vivid ‘Canary’ yellow are quite rare and beautiful, the finest of which generally comes from Sri Lanka.
Green Sapphire and multi colored green, yellow and blue Sapphire is also found, most famously from Chanthaburi Thailand.
Color Change Sapphire is one of the rareist and most sought after phenomenal gemstones. Color-Change Sapphire, exhibits different colors in different light. Color change Sapphires are blue in outdoor light and purple under incandescent, indoor light, or green to gray-green in daylight and pink to reddish-violet in incandescent light. Color Change Sapphires come from a variety of locations, including, Thailand, Vietnam, East Africa, Madagascar and Sri Lanka. The color-change effect is caused by the interaction of the Sapphire, which absorbs specific wavelengths of light, and the light-source, whose spectral output varies depending upon the illuminant. Transition-metal impurities in the sapphire, such as chromium and vanadium, are responsible for the color change.
Star Sapphire is also a very famous and rare phenomenal variety of corundum. Natural, fine Star Sapphires can be very expensive, with Blue Star Sapphire leading the way. The star appears in a translucent Sapphire due to fine rutile needles alignging themselves along the crystal axis at 60 degree angles, thus giving the appearance of a 6 rayed star. In a natural Star Sapphire this star affect will be visible only under natural sunlight or an intense beam of light.
Sapphires also occur in shades of orange and brown. Colorless Sapphires are sometimes used as Diamond substitutes in jewelry. Natural Padparadscha (pinkish orange) Sapphires often draw higher prices than many of even the finest Blue Sapphires. Recently, more Sapphires of this color have appeared on the market as a result of a new artificial treatment method that is called “lattice diffusion”.
The cost of natural sapphires varies depending on their color, clarity, size, cut, and overall quality – as well as their geographic origin. Significant sapphire deposits are found in Eastern Australia, Thailand, Sri Lanka, China, Madagascar, East Africa and North America. Sapphire and rubies are often found in the same geographic environment, but one of the gems is usually more abundant in any of the sites.
Sapphire as will all corundum is a very hard and durable gemstone. It is 9 on the Mohs Hardness Scale.
Sapphire is the Birthstone for September
- CATEGORY Gems - About