The history and knowledge of sapphire

Traditionally, the sapphire symbolizes nobility, truth, sincerity and loyalty. It has decorated the dresses of royalty, members of the clergy for centuries. Its extraordinary colour is the standard by which other blue topaz tanzanite gems are measured.

For centuries, sapphire has been associated with royalty and romanticism. The association was strengthened in 1981, when Prince Charles of Great Britain gave Lady Diana Spencer a blue sapphire engagement ring. Until her death in 1997, Princess Di, as it was known, charmed and captivated the world. Her sapphire ring has helped link modern events to history and fairy tales.

In ancient Greece and Rome, kings and queens were convinced that blue sapphires protected their owners from envy and evil. In the Middle Ages, the clergy wore blue sapphires to symbolize the sky, and ordinary people believed that the gem attracted divine blessings. In other times and places, people instilled sapphires with the power to protect chastity, make peace between enemies, influence spirits, and reveal the secrets of oracles.

In folklore, history, art and consumer awareness, sapphire has always been associated with the colour blue. Its name comes from the Greek word sappheiros, which probably referred to lapis lazuli. Most jewellery customers think that all sapphires are blue, and when jewellery and jewellery professionals use the word “sapphire” on its own, it normally means “blue sapphire”.

A special pink orangy sapphire colour is called padparadscha, which means “lotus flower” in Sinhala, the language spoken in Sri Lanka. The stones from Sri Lanka were initially the only ones labelled with this marketable name. It is not known how many padparadschas have been encrypted from the gravel of the Sri Lanka River throughout history. Sri Lankans have a special affection for the colour traditionally associated with their country.

The colour of sapphire

Sapphires come in a wide range of colours, and each colour has its own variations in quality. In general, the more intense the colour and the less distracting areas of unappealing colour, the more valuable the stone.

Colour has the most important influence on the value of blue sapphire. The most popular blue sapphires are velvet blue violet blue, in mid to medium dark tones.
Preferred sapphires also have a high colour saturation. The saturation should be as strong as possible without obscuring the colour and compromising the brightness. Sapphires with these qualities have the highest prices per carat.

At the other end of the price scale are commercial grade sapphires with a greenish blue colour or a strong presence of greenish blue. Pleochroism is a different colour seen in different crystal directions. Less valuable blue sapphires might be greyish, too light, or too dark.

The main categories of sapphire colours are: padparadscha, pink and purple, orange and yellow, green, colourless and black. Each category has its own colour range.

Fancy sapphires such as padparadscha are very beautiful. They generally have a high value per carat.

Their colour can be difficult to describe. Some people say that the colours of padparadscha sapphire should be called salmon or sunset.

Despite these different colour descriptions, gemmologists generally agree that the colours of padparadscha sapphire are intensely saturated and range from light orange to dark orange to orange-pink.

Pink sapphires vary from red to purple with low to vivid colour saturation and a lighter tone.

Purple sapphires are similar in colour but darker and always have purple as the dominant colour. They range from medium to black red-purple to purple with low to bright colour saturation.

Corundum appears in a range of yellow and orange hues that includes bright lemon, sweet peaches, and a vibrant tangerine.

In specific colour terms, yellow sapphires range from light yellow to dark green to orangey yellow with low to intense colour saturation. The best yellow sapphire is yellow to orange-yellow with vivid saturation.

Orange sapphires range from yellowish orange to reddish orange. The finest orange sapphires range from pure orange to red-orange with a medium tone and vivid saturation.

Green sapphires range from light to dark bluish green to yellowish green and are usually low in saturation. Green sapphire is readily available, but its colour is not very marketable. Its colour is sometimes described as khaki or olive. This is because stones tend to have low saturation or unappealing colour zoning.

Colour changing sapphires are corundum chameleons – stones that change colour under different lightings. Under daylight (fluorescent), the base colour of the typical coloured sapphire varies from blue to purple. Under incandescent light, it ranges from violently purple to strongly reddish purple. Some exceptional colour changing sapphires turn from green in daylight to reddish brown in incandescent light.

When gemstone experts judge sapphires to change colour, they describe the colour change as weak, moderate, or strong. The strength of the stone’s colour change is the most important quality factor that affects its value, followed by importance by the actual colours of the stone.

As with all coloured stones, the colour of the star sapphire has a great effect on its value. The most beautiful star sapphire has a sharp star with a highly saturated colour. If the colour is too light, it will not provide enough contrast for the star’s rays, and the star will be less visible.

Star corundum can be red, blue, black, Gray, purple, or yellow, virtually any colour under the sun. The term “star sapphire” encompasses all the colours of star corundum except red, called star ruby.

The new sources can produce materials that are very similar to those of conventional sources or with a slightly different appearance, but just as beautiful.

The clarity of sapphire

Several types of inclusions are found in sapphires. Among these are long thin mineral inclusions called needles.
The fine needles are called silk when they occur as the mineral rutile in intersecting groups.
Other sapphire clarity characteristics include mineral crystals, partially healed cuts that look like fingerprints, colour zoning, and colour bands.
Usually inclusions make a fewer valuable stone.
 The price can drop significantly if the inclusions threaten the durability of the stone. Although inclusions can increase the value of some sapphires.
Many of Kashmir’s most valuable sapphires contain tiny inclusions which give them a velvety appearance.
They scatter light, causing the coveted visual effect without negatively affecting the transparency of the gem.

Star rubies and star sapphires belong to the category of corundum. The starry effect is called asterism. It is caused by reflections from tiny, high-pitched inclusions that point in several specific directions. Stars usually consist of 2, 3, or 6 crossed bands, resulting in 4, 6, or 12 rays.

The most common stars have 6 rays, and stars with 12 rays are quite rare.

The best star is distinct, cantered on the top of the stone, and visible from a reasonable distance. The quality of the star should be the same when viewed from all directions.

The rays should be uniform and cross at the top of the stone. They should be straight, not blurry, wavy, or broken, and they should contrast strongly with the background colour. The star should also have an elegant “movement”. This means that when you rock the stone, the star should move smoothly across the surface.

The star corundum considered to be the most beautiful and the most expensive is semi-transparent, with just enough silk to create a well-defined star. Too much silk can adversely affect the transparency and also lead to poor colour, drastically reducing the value of the stone.

The cut of sapphire

Oval shapes with triangular and kite-shaped facets on the gem crown (upper part) and parallel rectangular facets on the gem pavilion (lower part) are very common for corundum of all colours.

The shape of a sharp sapphire influences the shape and size of the finished stone. The most common crystalline form of rough sapphire is a hexagonal barrel or spindle shaped pyramid. For this reason, finished sapphires are often deep or breeched.

To get the best overall colour, maintain the best proportions, and retain as much weight as possible, cutters focus on factors like colour zoning, pleochroism, and a stone’s lightness or darkness.

The colour zoning of different colours in a stone is a common feature of sapphire. Blue sapphire often has angular areas of blue and a lighter blue. To accommodate the colour zoning in some sapphires, cutters orient the concentrated colour to a location that provides the best colour visible in the cut stone.

In Sri Lankan sapphires, the colour is often concentrated near the surface of the crystal. If a cutter can orient the breech in the area of ​​concentrated colour, the stone will appear completely blue in the face-up position.

Pleochroism is a different colour in different crystal directions. Blue sapphires often have a blue-blue-purple and blue-purple verdict.
It is best to orient the cut so that the stone shows the violet blue colour when set.

Star corundum should be cut like a cabochon to display the asterism. The attractiveness of a finished stone depends on the orientation of the star and the symmetry, proportions and finish of the cabochon.

The cabochon should have an attractive appearance with the star being properly cantered when the gem rests on its base. The outline of the stone should be symmetrical.

For most stones, the top of the stone should be high enough – about two-thirds the width of the stone – to strongly focus the star. If it is too high, the phenomenon loses its graceful movement when the stone is tilted. Excessive height makes the stone difficult to climb. 

If the dome is cut too shallow, the star will only be visible from directly above. Black star sapphires, however, are prone to parallel breaks, so they are usually cut very flat to reduce the risk of damage.

A stone should not have excess weight below the waist which does not contribute to the optical effect or the reinforcing colour.

The characteristics of sapphire

1. Crystal system: Rhombohedral
2. Chemical composition: Aluminium oxide (Al2O3)
3. Colour: Blue, yellow, pink, green and colourless
4. Hardness: 9 on the Mohs scale
5. Specific weight: 3.80 to 4.00
6. Refractive index: 1.76 – 1.77
7. Dispersion: 0.018
8. Pleochroism: Blue-violet, blue-green

The different sapphire deposits

Most of the sapphires are found in alluvial and eluvial deposits. They are either originating from:

From a deposit of limestones (the most beautiful sapphires) as in Kashmir, Sri Lanka, Myanmar (ex-Burma) or Tanzania

Volcanic (less beautiful sapphire, but more numerous): Cambodia, Kenya, China, Australia, Madagascar, Thailand or Montana (USA)

In its native state, this stone is mainly present in humid tropical areas. It is mainly found in Madagascar (Ilakaka deposit), Sri Lanka and Burma but also in China, India, Brazil, Thailand and Africa.

The regions of Kashmir and Ceylon are the most famous for blue sapphires, their hue is purple for Kashmir sapphires and is a bright blue for those of Ceylon.

Sapphires and treatments

To improve the appearance of certain poor-quality sapphires – called GEUDA – it is possible to heat them. The sapphires will be heated to 1600 ° C in a colouring substance. This treatment will give the gem a more uniform and radiant colour. This treatment has on the other hand a major drawback, it damages or destroys the structure of the sapphire, but fortunately it can be detected by an experienced gemmologist.