Sapphire is the birthstone for September, a durable gem with a hardness of 9 on Mohs scale. Sapphire is a wonderful stone for all types of jewellery including engagement rings due to its wide range of colours and hardness. It is also the suggested gift for 45th and 65th anniversaries. Sapphire is a variety of corundum which in its purest form is colourless (white Sapphire). Traces of colouring elements produce the amazing array of Sapphire colours. Most of the Sapphire mined is of poor and industrial quality and only a small percentage is cut and polished into beautiful gems. Sapphire has a Specific Gravity of 3.99 – 4.01 and Refractive Index 1.760 -1.774 doubly refractive.
Ceylon Type Sapphire (Blue)
Ranges from very light blue to rich deep blue colour. The colour is due to trace elements of iron and titanium Subjective terms like cornflower blue are confusing and should be avoided. Descriptive terms eg. light blue with a hint of mauve are more useful. Currently this type of Sapphire is predominantly mined commercially in Sri Lanka and Madagascar with limited production in some African countries. Gemmologically t is not always possible to definitively determine which country a Sapphire originated in, so we describe these as ‘Ceylon Type Sapphire’ as they have a similar range of blue tones.
Australian Type Sapphire
Is typically a darker inky blue and similar material is also mined in Laos, China and minimal quantities in Thailand. Recently mining in Australia has been greatly restricted due to lack of water and lack of suitable material.
Is mainly mined in Sri Lanka and Madagascar and coloured by chromium. Pink Sapphire is a popular Sapphire colour, it is available in pale pink through to rich intense pink and is a good substitute for pink diamond.
Is available in a wide variety of shades from pale lilacs and mauves to deep magentas and rich purples. It is a very popular colour which derives its colour from vanadium and chromium. Purple Sapphire is mined commercially in Sri Lanka and Madagascar.
Orange, Apricot and Peach
These colours are occasionally found in Sri Lanka, Madagascar and Tanzania. These unusual colours of Spphire are popular but availability is limited.
Is really gaining popularity and is also used as an alternative to diamond. Its colour palate ranges from pale yellow through to golden yellow and occasionally rich orange. Production of Yellow Sapphire is limited and not all sizes and shapes are available. The yellow colour is due to small traces of iron. Yellow Sapphire is mined in Sri Lanka, Madagascar and Australia.
Is predominantly found in Australia and Madagascar and the colour is due to small traces of iron. Green Sapphire is available in light tones through to deep green and blue greens and parti-sapphires which have sections of blue, green and yellow.
Is a rare fancy coloured Sapphire currently mined in Sri Lanka and Madagascar. Padparadscha is Sinhalese for lotus blossom. Padparadscha Sapphire is a delicate blend of orangey-pink or pinkish-orange not just one or the other.
Is most valuable with a sharp, even 6 ray star in translucent deep blue. The price of Star Sapphire lessens as the colour becomes a lighter greyish blue, the gems become more opaque and the star becomes weaker and more diffused. The star in blue Sapphire is caused by light reflecting off intersecting rutile (silk) needles inside the gem. A brownish black star Sapphire is also available, it is opaque and less valuable than the blues.
Blue to blue – grey star Sapphire is mined in Sri Lanka, black brown is mined in Thailand and Australia and the deep opaque blue in Africa.
Colour Change Sapphire
Is rare; the gem changes colour in different types of light eg. blue in daylight to purple in incandescent light. This phenomenon in Sapphire adds extra appeal to the gem and is due to chromium being present in the crystal structure with titanium and iron.