Rubies, the gemstones for July, are beautiful. Their lovely red colour is stunning and they look so good set in yellow gold. Rubies are members of the corundum family, along with sapphires. They are a very hard stone, ranked as a 9 on the Mohs’ hardness scale, so ideal for use in rings. The colour of rubies can vary from a deep blood red to a pinkish red. Quality rubies are expensive but as I discuss below, there are a number of issues with many rubies sold today.

Rubies pair beautifully with other gemstones, particularly diamonds. The lovely Belle Epoque pendant below is a beautiful example of this.

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French Belle Epoche pendant with rubies and diamonds

The drop earrings below are a modern example of rubies used as a feature with diamonds.

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Diamond and ruby drop earrings

It is not just diamonds that rubies work with as can be seen in this lovely ‘Regard’ ring, set with an emerald, amethyst, diamond, and garnet.

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Victorian regard ring


Rubies have been confused with other red stones over the centuries. The red spinel is the main cause for confusion as it is a similar colour to the ruby and was often found close to rubies in mines. Many large famous red gemstones, like the Black Prince’s Ruby set in the Imperial State Crown of Great Britain and Catherine the Great’s Imperial Crown, are spinels but this was not discovered until the 19th century as gemmological knowledge developed.

Today, there are many challenges with rubies. A patent for synthetic rubies was granted in 1904 and now there are numerous methods for producing synthetic rubies.  For many years, rubies, like many other stones, have been heat treated to improve the clarity of the stone by dissolving internal inclusions. These treatments are permanent and durable. Less stable are treatments involving external coatings and diffusion of some sort.

Glass filled rubies are a real problem for purchasers though today. Glass filled rubies  are badly fractured stones that have been filled with glass. Classified by the Gemological Institute of America (GIA) as being composite stones rather than gemstones, they are widely available in shops and some online sites and yet disclosure about their nature is often missing or not complete.

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Glass filled ruby


Purchasers of jewellery with rubies in it need to really question the retailer about the stones used and read all statements made about the stones very carefully.