The Optical Illusion Enjoyed by Sapphire Engagement Rings

Sapphire engagement rings are highly desirable gemstones on the market, generally considered to be a more affordable alternative to the traditional diamond. However, sapphires do have other special attributes that make them a desirable and popular stone, such as their ability to change colour simply depending on what angle you look at them. This type of visual effect is known as pleochroic.

Arguably one of the more intriguing properties of many gemstones, this optical phenomenon is displayed by gems which appear to have different colours or depth of colour when viewed at different angles. Such a phenomenon is caused by differing absorption of light rays in doubly refractive crystals. Thus no singly refractive gemstones, like diamonds and garnets, can exhibit pleochroism.

This optical illusion is usually classified as visually ‘weak,’ ‘distinct’ or ‘strong’, and each gemstone typically exhibits one of the three grades. However, distinct colours are more difficult to see in pale or lightly coloured gemstones, but even the more noticeable colouring that gemstones can display goes largely unnoticed by the public – something you should consider while looking at sapphire engagement rings.

Sapphires are generally pleochroic, displaying a lighter and more intense colour when viewed at different angles. For instance, some pleochroic sapphires will appear blue from one angle and yet purple from another. Although sapphires generally only display two colours, there are some gems that show three colours, such as tanzanite, which can portray blue, purple and green.

However, this is not the only case of colour change known to occur in sapphires. Colour changing sapphires, a rare type, exhibit different colours in different lights, as opposed to angles. So, in natural light, such a sapphire will present as blue, but in artificial light, it will be violet. (Such a stunning phenomenon is also seen in the rare gemstone, alexandrite, although the colours differ.) Another cause for different colours in sapphires is colour zoning which forms from growth layers that build up during the formation of the stone. Colour zoning is responsible for certain sapphires having lighter and darker colours in different parts of a crystal. This is what makes some sapphire gemstones appear multicoloured, such as purple and blue.

If you and your partner have been considering sapphire engagement rings, you can thus expect this beautiful illusion to be present in the majority of stones. The decision you have to make is one based on personal preference and whether you admire this particular quality of sapphire engagement rings enough to look for a stone that has a strong pleochroic effect.

Frederick Holm is staff writer for of the F&L Designer Guides, compiled and written to help consumers choose a unique engagement ring design. From a diamond to a sapphire engagement ring from a princess cut to a platinum band, we have ideas and opinions covering all the options. Offering advice, tips and suggestions on how to choose that perfect ring, F&L will accompany you on every stage of your search to find the right designer.

Writer and Online Marketing Manager in London.