Blue is the colour of the ocean, a summer sky and a winter night so no surprises then that sapphire rings outstrip emerald rings and ruby rings in popularity. So what makes a sapphire, a good sapphire? A rich blue bright with a lively appearance and good clarity; not heavily included.
Sapphires and rubies belong to the family of corundum. Corundum is the second hardest gemstone to diamond and it is found in Australia, Kenya, Madagascar, Myanmar, Tanzania, Thailand and Sri Lanka. Sapphires come in all colours except for red as they are called Rubies. Blue sapphires gain their colour from a combination of Iron and Titanium. There are a lot of different types of inclusions in gemstones. Inclusions can be either liquid, gas or crystals, they were trapped in the gemstone when it was formed. The possibilities of inclusions are endless and sapphires are no exception, below is a brief look at the types of inclusions that are found in sapphires from the particular localities.
What are typical sapphire inclusions?
Indian ( Kashmir) Sapphires:
These can look milky due to very small inclusions: Colour zoning, Zircon crystals, Stress fractures and Negative crystals.
They can be dark but generally have a good colour. There can be long inclusions; rutile and apatite, Convoluted feathers, Silk and Hexagonal colour zoning.
These have different colour zoning with inclusions of silk, feldspar, hornblende, spinel and uranium.
Sri Lankan sapphires:
Sapphires feature crystal inclusions of different types and healed fractures that can have the appearance of fingerprints.
These can show red crystals inside and crystals that have healed fractures surrounding them.
USA sapphires from Montana:
Montana sapphires have crystal inclusions of other gemstones such as garnet, rutile, calcite and pyrite.They show hexagonal colour zoning.
They can be very dark, looking almost dark blue, green or black.They exhibit strong colour zoning, and crystals with haloes.
How are Sapphires treated?
Both sapphires and rubies are often heat treated to improve the colour even of a synthetic one. A lot of sapphires are what is called “diffusion treated” to add colour to poorly coloured sapphires. Some fractured sapphires may be filled. The stones are coated with a compound and then heated to very high temperatures to induce the colour. In blue sapphires it is iron and titanium that causes the blue colour.
Can you tell if your sapphire is synthetic?
Well you might not be able to tell! There are two ways synthetic sapphires are made; a method called verneuil flame-fusion and a system called flux melt. It is complex to get into how they are made but here are the signs that you might have a synthetic sapphire. Verneuil flame fusion sapphires have growth lines, these are different colours where the sapphire “grew” they are curved as opposed to angular. There can also be gas bubbles present.
To complicate matters the synthetic sapphire could also then be ‘heat treated’ to give the appearance of natural sapphires so there can be evidence of healed fractures and a reduction of curved growth lines. Flux melt sapphires can have platinum platlets, angular growth zones ( which natural sapphires can also have) and flux particles in comet like patterns. Cavities filled with flux and healed fractures.
Above considerations of value, it is important that you buy what you love! While I admire the deep blue of the most expensive sapphires I am drawn to the deep dark night sky sapphires and the watery blue of pale sapphires.