Pink sapphire is a member of the corundum family of gemstones (which also includes ruby) and is formed from two chemical elements, aluminium and oxygen. These elements are the “ingredients” required to form sapphire crystals. Although pure corundum is colourless, when trace elements of chromium are present during the crystal formation, the result is pink sapphire.
Pink Sapphire Properties:
Refractive Index - 1.762 to 1.778
Birefringence - .008
Dispersion - .018
Optic Character - Uniaxial
Optic Sign - Negative
Specific Gravity - 4.00
Hardness - 9
Cleavage - Poor
Fracture - Conchoidal to Uneven
Lustre - Vitreous to Sub-adamantine
Transparency - Transparent to Opaque
On the Mohs Scale of Hardness, sapphire is rated as a 9, making it second only to diamond on this scale, which is a measure of its resistance to scratching. This is one of the reasons why sapphire is a popular choice in jewellery that is worn regularly, such as engagement rings.
The majority of pink sapphires on the market today have been heat treated in some way to improve their colour and/or clarity. Heat treatment in a gas or electric furnace is now a standard practice in the gem industry.
Pink sapphire can be found in a number of other locations around the world including Madagascar, Sri Lanka, Myanmar, Australia and Tanzania.
There is a belief that pink sapphire crystals can strengthen the emotional well-being of the person wearing jewellery made with the gems by removing emotional obstacles from the wearer's past and releasing painful or distressing experiences. Removing these blockages may allow the person to experience more positive energy, promoting emotional healing.
Sapphires have been referred to as gemstones of truth and honesty, enabling people to make better and more beneficial decisions in their lives.
Sapphires are crystals of the mineral corundum, made up mostly of atoms of aluminium and oxygen in a 2 to 3 ratio (Al203). The chemical bonds of aluminium and oxygen are particularly tight, making sapphire one of the hardest minerals known with a rating of 9 out of 10 on the Mohs Scale of Hardness. Sapphire is second only to diamond in hardness.
Corundum crystallizes in the trigonal crystal system and is typically found in three common shapes (habits); spindle-shaped bipyramids, columnar hexagonal prisms and tabular prism and rhombohedron combinations although a myriad of habit combinations are possible depending on the locality and colour. The crystals can take a range of forms, including bipyramidal, barrel and pinacoidal.
Sapphire and ruby are resistant to heat, light and chemicals.
Sometimes there is a ‘star’ effect (asterism) present in rubies and sapphires (which are polished in the cabochon style to show the effect to best advantage). Like cat's eye (chatoyancy), the effect is due to fine parallel fibres or crystals (usually rutile, but sometimes hematite).
The host rocks for sapphire are dolomotized limestone, marble, basalt and pegmatite. Ruby is formed in metamorphic dolomite marbles, gneiss and amphibolite. Rubies and sapphires are often mined from secondary alluvial deposits rather than from the primary rock, with the vast majority of sapphires and rubies (thought to be over 80%) being produced by artisanal and small-scale mining (ASM) operations.
Some of the most well-known sapphire producing countries are Sri Lanka (Ceylon), Madagascar (Ilakaka), Tanzania (Umba), USA (Montana) and Australia (Queensland). Historically, many impressive sapphires were discovered in Kashmir at the end of the 19th century, whilst Burma (Myanmar) produced some of the world's finest rubies for a long period. The current leading producer for ruby is Mozambique.
Natural rubies and sapphires often contain a profusion of microscopically small canals or crystals, known as ‘silk’ that reflect the light and produce a whitish sheen, thereby detracting from the beauty of the gem material. Typically these crystals consists of rutile (titanium oxide).
Therefore a large percentage (some people quote up to 90%) of corundum is heat treated to improve the colour and clarity. This can be a very simple, relatively low temperature treatment using traditional blowpipe or other basic techniques. It could also be a gas or electric furnace with temperatures going as high as 1800C or more. The melting point for corundum is just over 2000C.
By heating the stones steadily and progressively through increasing temperatures over a period of hours or even days, it is possible to improve the overall clarity of sapphires and rubies through the partial or complete dissolution of the rutile needles or intensify the colour of blue sapphires as the titanium is slowly diffused into the stone. This technique was used extensively and with great effect by gem traders from Thailand, who converted seemingly worthless "geuda" corundum from Sri Lanka into fine blue sapphires during the 1960s.
Of course, there is always a chance that heating can cause the sapphire to crack or explode and, for that reason, heat treatment is usually performed on rough material rather than faceted.
After heat treatment, it is sometimes possible to see the so-called "snowball", "cotton ball" or "halo" effects caused by crystal inclusions or trapped gas bubbles expanding during the heating process. Whilst these can indicate possible heat treatment, they should not be considered as conclusive evidence.
You can view our range of ethical blue sapphires in our gemstone store. They are fully traceable, loose gemstones that have been responsibly sourced.