Coloured Gems

Sapphire

Sapphire is the gem variety of the mineral corundum. It is an extremely hard and durable gemstone, second only to Diamonds on the Moh's hardness scale. Sapphires are available in virtually all colours but red; Red Sapphires are known as Rubies. We also have a large selection of pink sapphire.

Blue Sapphires are the most valuable, followed by Pink and Padparadscha Sapphires. Padparadscha Sapphires have orange pink or pink orange coloration and rival Blue Sapphires in value.

Sapphires over two carats, particularly Red (Ruby), Blue, Pink, and Padparadscha Sapphires, are very rare and valuable. Sapphires are typically heated to enhance colour. The treatment is stable and permanent. Some Blue Sapphires are not heated; these stones command a premium price.

We obtain Sapphires from Sri-Lanka (Ceylon), Thailand, Cambodia, Myanmar (Burma), Vietnam, Madagascar and Africa. Madagascar and Sri-Lanka are our principal suppliers of Pink Sapphire.

Ruby

Ruby is a variety of the mineral Corundum. A Ruby is actually a Sapphire of red colour. It is an extremely hard and durable gemstone, well suited for all jewellery applications. Rubies of Thai and African origin tend to be darker and have better clarity than Burma Rubies.

Top quality Rubies are highly prized, and in larger sizes are frequently valued above all other gemstones, including Diamonds. Rubies over two carats are extremely rare and valuable. Generally, Rubies with true red colour are valued above those that are darker, with purple hue.

Emerald

The Best and Most Valuable Colour

Many people seem to believe that the darker the emerald the better, just as many seem to believe the opposite. Neither of these opinions is correct. If you think, even briefly, about this it becomes obvious why. A very dark emerald would appear black, and would not be very attractive or desirable. The darkness often being caused by inclusions. An extremely pale emerald would be colourless, and not particularly attractive or valuable.

As usual, the truth lies between the two extremes. The most desirable emeralds are generally those with an intense grassy green colour, plenty of sparkle and life, and free of any inclusions. Some experts say that a dark velvety green is the most valuable.

Ultimately which is "best" is a subjective matter, and personal preference is important. Our usual advice to potential customers is to buy whichever colour of emerald they personally find the most attractive. We also think it's slightly sad that we need to give this advice. Buy what you like, using your own judgment, rather than allowing yourself to be a slave to fashion and buying what you think will impress other people.

The main choice in the colour of emeralds depends largely whether you prefer lighter but brighter stones, or a deeper more intense colour.

Oiling or Filling

The vast majority of emeralds are oiled, that is to say, immersed in oil which fills the many cracks and fissures to which emerald is prone. This has the effect of reducing the visibility of the inclusions, and improving the clarity of the stone. Sometimes oiling also improves the colour. Green coloured oil is sometimes used to enhance the stones natural colour, there are also other fillers used which are more permanent than oil.

Because oil filling of emeralds has become almost universal, it is generally not considered essential to disclose this fact. We suggest that anyone wishing to buy a high quality or expensive emerald should request a gemstone laboratory certificate stating that the stone is natural and not oiled, but be prepared to pay extra for a certificated stone.

Most modern emeralds are likely to be oiled at the mines, and again at the cutters.

Cleaning

Emerald jewellery can be carefully cleaned using warm soapy water, or detergent, rinse thoroughly afterwards as detergents can cause dermatitis and allergic reactions. Enzyme cleaners should be avoided for the same reasons. Brushing with an old toothbrush to remove dirt and grease will also help. Cleaning agents containing chlorine may have a detrimental effect on low carat gold alloys, so are best avoided.

We stress that reasonable care should be taken when cleaning emeralds, as washing with strong detergents could cause any oil to be diluted or removed, requiring the stone to be re-oiled.

Emeralds do not like excessive heat, and although they can tolerate temperatures above 100C° (the boiling point of water), it is advisable to use warm water rather than hot water, to reduce the dangers of thermal shock.

It is not advisable to clean emeralds in an ultrasonic tank. We sometimes risk it with our own stock, but we would never clean a large or valuable emerald that did not belong to us, in an ultrasonic machine.

Repair Work

Because of emeralds sensitivity to high temperatures and rapid temperature change, it is somewhat risky to carry out soldering close to emeralds when carrying out jewellery repairs. It is possible for emeralds to be coated with borax, or proprietary heat-shielding material while carrying soldering work on the jewellery in which they are set, but this must be done carefully, and if the emeralds are large or of very high quality, it is better to unset them before carrying out repair work involving heat. Naturally this itself carries some degree of risk. For this reason, it is best to treat emerald jewellery with greater care and respect than for tougher stones such as diamond, sapphire or ruby.

The mounts should be of good quality alloy such as eighteen-carat gold or platinum, not nine carat. Expect to pay more for repair work on emerald jewellery than for similar work on other stones.

Tanzanite

Tanzanite is the name given to transparent blue Zoisite, and was discovered in Tanzania in 1967. Tiffany & Co. of New York introduced Tanzanite into jewellery in 1969. Colour: Usually blue, lilac blue, or deep violet blue, but other colours are possible including green, yellow, pink, brown and khaki. These colours and also paler blue stones are often heat treated to produce the preferred deep blue colour. Tanzanite is slightly fragile, and can fracture badly, ultrasonic cleaning should be avoided, but otherwise it is very suitable for jewellery, being a very beautiful stone, similar to sapphire. Kellerwood have a strong collection of fine quality tanzanite jewellery.

Tourmaline

Tourmaline is generally thought of as green, but can be almost any colour for example we have a collection of pink tourmaline, indeed some tourmalines display two or more colours within the same crystal. Because of the naturally occurring shape, tourmalines are often cut as long baguettes, emerald cuts, or ovals. Large size tourmalines are more relatively common compared with other gemstones, so they are ideal for large jewellery pieces. As with all gemstones, the most attractive colours and qualities are more expensive than lower qualities, and large desirable pieces are not cheap.

Colour

Tourmaline exists in more colours than any other gemstone. The most common colour is a dark green, but bright green chrome tourmalines are seen, as are blue, red, pink, orange, yellow, colourless, brown, violet and black.