When looking at buying an engagement ring you should always consider sapphires. Sapphires are one of the most beautiful stone in the world yet mystery surrounds the nature of their quality and cost. Here I am going to look at all the factors that make up the value of a sapphire and give guides on best practice for purchasing them. Sapphires are a member of the Corundum family of Gemstones. What many people do no know is that Rubies and Sapphires are actually the same stone. The only difference is the trace mineral elements that give a Ruby its colour versus that which gives blue sapphire its colour. The most highly prized colour for sapphires is a rich velvety almost violet blue. Corundum is composed of aluminium and oxygen. In its natural state it is colourless but most contain trace elements. Trace elements of Iron and Titanium cause sapphire to have its blue colour. The more iron present in the stone the darker the blue.
Certain areas in the world are famous for their quality sapphires. Stones located at these regions can command a huge premium due to their rarity. Sapphires that form in basaltic geological environments tend to be richer in Iron and as such have a darker colour. Cambodia, Thailand and Australia are regions best associated with darker Basaltic sapphires. Famous Kashmir sapphires form where marble comes in contact with an intruding pegmatite. The trade use the term “Kashmir” to describe a very specific violet to almost pure blue hue. This is often referred to as “Cornflower” blue.
The mine in Kashmir was discovered in the 1800’s following a landslide in the Kudi Valley in India. The mine became the property of the Maharaja and by 1887 the original mine was depleted. Kashmir is generally considered to be the finest example of the blue hues. These stone command enormous premiums.
In November 2013 in Sothebys Geneva The Richelieu Sapphires sold for US$ 8,358,520. These earrings were each set with cushion cut sapphires each weighing 26.66ct and 20.88ct respectively.
Also in Sothebys Geneva in November 2013 a 114.74ct Burmese Sapphire fetched $7,223,285
“Burmese” sapphire tend to refer to a colour of stone that is slightly violetish blue to blue hue. The blue tends to be more “inky” than Kashmir
“Ceylon” and “Sri Lankan” refers to sapphires that have violetish blue to blue hue, with slightly grayish to strong saturation. The lighter tone of these stones tend to mean that they have a greater brilliance. “Thai” and “Australian” sapphires usually have a medium to dark tone with a greenish blue overtone.
In May 2011 Christies Geneva sold a 130.5ct Sapphire set in a brooch for $7,127,453
Christies Geneva sold The Star of Kashmir in May 2013 for $3,484,142
Unlike diamonds sapphire treatments are quote common in the trade. It is estimated that over 95% of sapphires that you see have been subjected to some kind of treatment. The most common treatments for sapphires are Heat and Lattice diffusion. Click on the GIA link for an in depth look at these treatments.
Heating is by far the most effective way to improve a sapphires colour. Blue sapphires are heated to temperatures ranging from 850˚F to 3500˚F. They are kept at these temperatures from anywhere from an hour to 14 days.
Lattice diffusion involves the sapphires being packed into a crucible containing colouring agents like Titanium and Beryllium. This results in a thin layer of colour around the stone. This type of treatment is present at the lowest and least expensive level of the sapphire market.
If a sapphire is being sold to you as being “un treated” make sure you obtain an independent laboratory certificate stating that. Generally we do not sell sapphires as being untreated unless we also have a cert to back it up as this can generally only be detected under laboratory conditions.
Below are some videos of sapphire rings we have available at CM Weldon in the Powerscourt Townhouse Centre