Sapphire

In the last section of the gemstone guide, we took a look at Rubies. This section of the Gemstone Guide gets a bit more technical as we take a closer look at sapphires

The sapphire is also a member of the corundum family, and in general any corundum that is not red will be labelled a sapphire. Besides blue, other common shades are yellow, pink, purple, orange and green. These shades are less highly valued than the truly prized blue form of the stone.

As colouration of the stone varies greatly, sapphires are primarily valued based on carat, origin, treatment, weight, hue and then clarity. Depending on the market and the client, the level of value assigned to a given shade will vary. Sapphires can be natural (simply extracted from the ground and polished) or colour enhanced, with natural sapphires obviously commanding the higher price tag on a like-for-like basis.

Origin

Origin of a sapphire can greatly influence the value of it, especially if they are rich blue and clean. The true Cornflower Blue of a No Heat Kashmir sapphire will fetch the highest prices, but are exceptionally rare, it is the equivalent of the Pigeons Blood Ruby from Burma. Royal Blue Burma Sapphire is next, followed by Royal Blue Sri Lanka Sapphires. On a like-for-like basis, the unheated sapphire will always be worth more than a heated sapphire.

It is wise to explore colour trends of the sapphire. Lighter colours alternate with darker stones for market preference. At the moment Vivid Royal Blue, both heated and not, command the highest prices generally speaking. Cornflower blue is the colour used to describe the colour of a sapphire from Kashmir and in fancy coloured sapphires, a rare colour shading of salmon pink with orange undertones, known as Padparadscha, is commanding high values in its natural and untreated state.

Most sapphires, regardless of hue, will receive heat treatment, unless sold otherwise. Diffusion treatments can enhance the hue, but are not universally accepted as a good option. If diffusion is used it must be disclosed and this can reduce the value of the sapphire. Sapphires are traditionally found in South- east Asia and Australia. Lesser mines exist in Africa, China, and the United States.

Blue Sapphire Facts

Hardness: 9

Colour: Blue, also with secondary hues of violet and green. Pure blue sapphires and blue sapphires with some violet hues are most desirable.

Colour in Blue Sapphire occurs in zones: rich colour alternating with colourless areas. Sapphires that show zones with the loupe, (x10 magnification) may be perfectly eye clean. Stone cutters try to reduce the effect of zoning and thus stones can appear uneven, although this can be masked in the setting. Symmetry faults in sapphire are accepted, especially if they are below the girdle.

Heating to improve colour is common. Sapphires are the birthstone for September and have been prized as great gemstones since 800BC. Rulers of ancient Persia believed the sky was painted blue by the reflection of sapphire stones. The sapphire symbolises purity and wisdom and was traditionally a favourite stone for kings and priests.

Armed with a little more knowledge, the next engagement ring you sell might be a sapphire ring.