Ancient Persians once thought that the world sat on sapphires, turning the sky blue. Often associated with royalty and scarcity, sapphires are prized for the intense, vivid blue color that is unmatched by any other gemstones. Lustful and durable, sapphire is one of the most popular gemstone in the world, and the rich blue color is why this stone is one of my favorite.
A variety of corundum, Al2O3, trace impurities in the trigonal crystal structure can give a wide range of colors. Although known for blue, modern classification of sapphire now consists of every color besides red. Red corundum is better known as ruby.
Colorless, white, violet, green, yellow, orange, pink, purple, gray, brown, and even black can be found; these non-blue colors are known as fancy sapphires. Fancy sapphires are designated with a color prefix, like yellow sapphire for example. However, blue is still the preferred color, especially those with strong, vivid color saturation of medium blue – although yellow, orange, and pink hues are gaining popularity lately.
Traces of iron and titanium give the stone the color of blue, pink, and purple. Iron and vanadium gift the gemstone with the color of orange. By themselves, iron turns the stone yellow and green, chromium gives pink and red, and vanadium displays violet.
The standard blue that all are judged against is “cornflower” blue, or Kashmir blue, which is a an intense and velvety luster blue that not too light or dark. Yogo sapphires from Montana, USA and Mogok sapphires from Myanmar can also display this superb color naturally. One rare, and very valuable, non-blue color is padparadscha – word for lotus flower in Sinhalese – that displays an exotic color between pink and orange.
Like many other colored gemstones, sapphires often have inclusions but generally possess higher clarity than rubies. In corundum, silk-like needles, called rutie, can exist as inclusions that can lower the transparency of the crystal. However, dense, parallel groupings of rutie can refract light to grant asterism called a star sapphire. The star formed is commonly 6-pointed but 12-pointed star sapphire have been known; one of the most famous star sapphire is the Star of India. Furthermore, extremely fine rutie throughout the stone is said to create the enchanting Kashmir blue color; too much rutie, however, and gray becomes more prominent.
Another property is the ability to change shades when viewed at different angles and light source, or pleochroism. As such, keep in mind the desired color and occasion of use: outdoors, indoors, evenings. In general, blue in daylight and slight purple under fluorescence light.
Having a Mohs rating of 9, sapphire is one of hardest stone, second only to diamond. Because of its durability, this magnificent gemstone is perfect as an everyday jewelry and suitable for every jewelry piece. Rings being a popular choice. In fact, sapphire is the engagement stone for Princess Diana and Kate Middleton; truly a stone of royalty.
Natural gemstones with good color are very rare and expensive. As such, sapphires are usually heat treated to enhance the color, increase clarity, and reduce inclusions. Besides heat, diffusion and beryllium are two other common treatments. Diffusion is used to give a deeper blue or enhance the effects of a star sapphire. Oh the other hand, beryllium treatment is used to reduce blue tones but creates stunning bright orange and yellow sapphires.
On the other side, we have synthetic gemstones. Unfortunately, synthetic sapphire, or lab sapphire, is common using the Verneuil process; only experts will be able to tell the difference between natural and synthetic. Due to their hardness, they have many industrial applications so synthetic sapphires will always be prominent in the market.
Fine quality of stones are mined in Sri Lanka, Myanmar, Thailand, Cambodia, Australia, Madagascar, Tanzania, and United States. Sri Lanka. Madagascar, and Tanzania are the leading producers. Sadly, the region, Kashmir, that set the standard for sapphire have been mostly dried since the 1920s. Areas that can produce sapphires that comes close, or even match, those from Kashmir are Montana in USA, Pailin in Cambodia, and Mogok in Myanmar. Australia and Thailand produces deep blue stones with a slight tint of green, while Sri Lanka produces pastel blue stones.