Identifying a sapphire- Sapphire is easy to distinguish from other similar-looking gems

Sapphire is any form of gem-quality corundum, other than red (which is the ruby). Next to diamond, it is the second hardest mineral on earth.

Sapphire lacks cleavage, but it can exhibit an uneven fracture. It belongs to the trigonal crystal system, structured with four axes and three planes of symmetry. However, the crystal form may vary depending on the origin of the specific gem.

Sapphire is easy to distinguish from other similar-looking gems (such as beryl, zircon, tourmaline and others) by its superior hardness and durability. This is in spite of the fact that many other gemstones share a similar colour and lustre.

 

Gemological properties

Mineral: Corundum

Chemistry: Al2O3 (aluminum oxide)

Crystal System: Hexagonal

Density/Specific Gravity: 3.95 – 4.03

Mohs Hardness: 9

Refractive Index: 1.762 – 1.788

Birefringence: 0.008

 

Buying a sapphire

Sapphire colour

As you might expect, blue is the most famous and valuable colour variety of sapphire. Burmese and Kashmir sapphires, not often seen on the market today, are highly prized for their intense blue colour. Today, Sri Lankan and Madagascar sapphires are the most common, and these range in colour from light to dark blue.

The intensity of blue is the most important factor in the desirability of a blue sapphire. A small stone with excellent colour will generally fetch a higher price than a huge stone with a washed-out colour. A rich, bright blue is the most desirable colour, rather than a blue that is too dark and inky, or too washed-out. However, a lighter blue may possess a greater brilliance that is not generally found in darker stones. Colourless sapphires are fairly rare, as there will be at least a hint of colour in most stones. Blue is considered the default colour when referring to sapphires, and all other colours are called ‘fancy sapphire’.

Trace impurities are the colouring agents in sapphires, which in blue sapphires are generally iron and titanium. Other colours of sapphire are formed by different minerals, or minerals in different trace amounts. Heat treatment can product an intense golden yellow colour, and beryllium treated sapphires can be a brilliant bright yellow. Padparascha sapphires are a pinkish-orange colour, and are particularly rare and prized by collectors.

Natural daylight is the best way to view sapphires, as artificial light can make them appear darker. It can even make them appear less attractive than they actually are in natural light.

Sapphire clarity and lustre

Sapphire can be transparent to opaque, but transparent gems are the most valuable. Some translucent materials will be cut into beads or cabochons instead of gems, but opaque materials have very little gemstone value. Sapphires have an attractive, vitreous lustre.

Sapphires, as a rule, are cleaner than ruby, and it is thus possible to find eye-clean stones. However, large eye-clean stones in ideal colours can be quite rare. In some cases, extremely fine silk through the stone can enhance the value of a sapphire, as it can cause a velvety blue colour and the asterism seen in star sapphires. However, too much silk gives the gem a greyish hue and thus renders it undesirable.

Sapphire treatment

Heat treatment is the most common treatment for sapphires, but unheated specimens can also be found. Stones are heated – usually before they are cut – to between 1700 and 1800 degrees Celsius for several hours. Rich blue, unheated stones can command very high prices, as the vast majority of sapphires today are heat treated. Occasionally, diffusion treatment is used, but this is more common for star sapphires. Beryllium is used to treat sapphires to create bright orange and yellow colours that used to be very uncommon. However, all sapphire treatments should be disclosed by the dealer.

 

Gemstone care

The best way to clean sapphire is using a soft cloth or brush and warm, soapy water. It should then be rinsed to remove residue. Avoid using harsh household cleaners on your sapphire, as these might cause corrosion. In addition to this, extreme heat fluctuations can cause your sapphire to change colour.

Sapphire jewellery, as with all jewellery, should be removed before playing sports in order to protect it. When you are storing sapphire gemstones, wrap them in a soft cloth and/or keep them inside a fabric-lined jewellery box.

 

Sapphire history and lore

Sapphire is the September birthstone, and is considered to be the stone for Taurus. For those who believe in the healing power of gemstones, wearing a sapphire is thought to protect a Taurus’s mental health.

The sapphire has been used to symbolise truth, sincerity, loyalty and peace throughout history. It has also been believed to be a talisman to protect against evil spirits. Star sapphires used to be regarded as charms to protect travellers, and were considered so powerful that their protective power would continue even when the sapphire had been passed on to another owner.