How do Sapphires get their Colours

Sapphires are gemstones that are primarily valued, in addition to their rarity-for their colour. Sapphires are best known for their most popular colour variety: blue. However, these gemstones in addition to the famous blue are found in a variety of colours. In fact, an argument can be made that sapphires can be found in virtually every colour that is found on the spectrum. To understand the character of these colours and what makes them different, it is first important to understand what give sapphires their colour. Sapphires are corundum minerals that are found in countries such as Myanmar, Ceylon (Sri Lanka), Thailand and Tanzania. Though there are newer sapphire producing nations entering the field, like Australia and the United States, with its Montana range of sapphires. The colour present in a sapphire it is interesting to note, is the result of the impurities that lie within them, which takes us to the subject of trace minerals and their role in sapphire colour.

The Role of Trace Minerals

The mineral corundum in its natural state is colourless. Thus the colour that is present in a gemstone like sapphire, is due to its ‘allochromatic’ state: which refers to the accidental addition of colours via external factors. Notably, other mineral impurities or elements enter the gemstone in the course of its development under the surface. Since the corundum crystal contains a lattice structure (the structured arrangement of atoms), which determine its natural colourless state; the presence of various elements at smaller levels, disrupts the native lattice structure of the gemstone: causing light that hits the stone to be absorbed in a certain way, thus contributing to its various colours. As colour scientists will explain, colour that is visible in the world is a function of the wavelengths of visible light. With longer wavelengths verging on the colour red, whilst the shorter ones veering closer to purple. In sapphires, the crystalline structure that is affected by the presence of various trace elements determines its various colours.

Blue Sapphires

The famous blue sapphire owes its popular colour to the presence of titanium and iron in the crystal structure of the sapphire. The presence of these elements at varying degrees, and located in various parts of the gemstone contributes to its distinct saturation, which in the case of the blue sapphire, also contributes to its varying tones the blue, which differ from gemstone to gemstone, but also at varying colour ranges (e.g. Cornflower blue, Royal blue sapphires). In sapphires, the elements which contribute to its colour are not always dispersed throughout the gemstone. So the quality of the blue, in blue sapphires will vary upon the strength and dispersion of trace element present within a gemstone. Blue sapphires as the most popular variants of sapphires are found around the world, with top-quality sapphires coming from countries such as Myanmar, Thailand Ceylon (Sri Lanka). The latter, owing to its large supply of coloured gemstones, is notable for having the widest range of blue sapphires, and is home to the more elusive Cornflower blue and Royal Blue sapphire varieties.

Pink Sapphires

Pink sapphires can be considered a variant of rubies. However, the key difference lies in the lower levels of the trace element chromium. As there is a fine line that distinguishes a pink sapphire from the red: In the latter, where the higher chromium concentration in the corundum, makes the gemstone a ruby. The exact colour distinction between rubies and the variety of pink-reddish sapphires are a matter of debate even among gemologists. However, when it comes to pink sapphires the notable presence of a pinkish hue that does not contain the darker tones of red, is what sets it apart. If one goes into the science of colour, pink is actually considered a version of red. In the optics of colour, where wavelengths are used to determine the nature and function of colour, pink is known to have longer wavelengths. So when it comes to pink sapphires, the gemstone holds something of a middle ground in the colour range. Unlike the stronger blue tones of the blue sapphire or the deeper reds of the rubies, pink sapphires, like the colour pink hold that charming in-between position.

Yellow Sapphires

The key factor that gives rise to yellow sapphire is the presence of iron. However, this particular colour can also be induced due to the effects of natural radiation the stone may endure over time. Which can affect the type of yellow the gemstone carries. Yellow sapphires, like all coloured gemstones, come in a variety of shades, which gave given rise to a number of yellow sapphire varieties. Yellow sapphires can be found in lemon yellow shade, to the darker sunflower shades. Yellow sapphires are gaining in popularity more recently especially in the Subcontinent. Whilst these are cheaper than the top blue sapphire varieties, they are valued for their colour, which, along with the orange sapphire variant is respected in the Vedic/Hindu traditions for their mystical qualities.

White Sapphires

White sapphires differ from other gemstones in the corundum family in that they are colourless. The result of the notable absence of other elemental impurities within the crystalline structure of the stone. The embodiment of the allchromatic corundum, this variety of sapphires is those that have managed to evade the accidental infusion of other elements in the course of their long development. In its pure state, this type of corundum only contains aluminium and oxygen atoms which contributes to its colourless or white character. White sapphires are an interesting addition to the sapphire range since until recently the key selling point of sapphires has been their colour. However, given the rise of sapphires as competitors to diamonds in the fine jewellery range, it is only natural that white sapphires be viewed as real alternatives for the precious colourless carbon-based gemstones.

Rubies (Red Sapphires)

The highly sought after rubies are interestingly also made from the mineral corundum. With varying levels of concentration determining its purplish red to a deeper red colour. The element chromium is what makes rubies red. The term red sapphires is not a common one is owing to the fact that corundum that is naturally found with high levels of chromium is a rarity in many of the top gem producing nations. Rubies differ from other variants in the sapphire family due to their unique colour: red. Which are interestingly found in a variety of shades that veer closer to pink or purple. However, the challenge is in finding a gemstone that is high in chromium and is devoid of other trace minerals. So the colour value of rubies increases with the greater concentration of the colour red, and notably on how it differs from the pink and orange sapphire variants.