Sapphire is the birthstone for September, the gem for the zodiac sign Virgo and the 45th wedding anniversary gemstone.
A popular choice in jewellery due to its exceptional brilliance, range of colour and hardness (9 on Moh’s scale) While most commonly thought of as blue, sapphire actually occurs in a wide range of colours, including pink, purple, orange, yellow, green and brown. (Sapphire is every colour of the mineral corundum except for red, which is ruby.)
Blue Sapphire is still the most sought after and the most desirable blue is the intense, rich pure cornflower blue. The saturation should be as strong as possible without darkening the colour and compromising brightness. Darker or lighter blues are less valuable, though light blue sapphires often have greater sparkle or brilliance than darker blue stones. Many sapphires have pleochroism, (different colours are visible in different crystal directions).
Padparadscha Sapphire is a very rare sapphire with a pinkish-orange hue.
Natural Sapphire is mainly pale and light in colour and only a small percentage have vivid and intense colours without some type of enhancement, such as heat-treatment. Colourless sapphires are quite rare. In general, the more intense and even the colour, the more valuable the stone.
Inclusions are common in sapphire which can vary from highly transparent to opaque. Clarity characteristics in sapphire include mineral crystals, partially healed breaks that look like fingerprints, colour zoning (areas of different colours), and colour banding, (areas of lighter and darker shades). Blue sapphires with extremely high clarity are rare, and very valuable. Inclusions which reduce transparency generally also lower the sapphire’s value.
Cut varies widely as the shape of a rough sapphire crystal decides the finished stone’s shape and size. Cutters try to achieve the best overall colour by focusing on colour zoning, pleochroism, and the lightness or darkness of a stone, while maintaining the best proportions and retaining the maximum weight. Sapphires are cut in a wide range of facetted shapes though ovals, cushions, and rounds are most common. Cabochons cuts are mainly used in translucent stones or for stones with visible inclusions. Sapphires that have the optical phenomenon of asterism (the star effect caused by the intersection of needle-like inclusions) are always cut as cabouchons.