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August Birthstone - Peridot

It is time for this month’s birthstone run down, and you August babies are seriously lucky with your gemstone: peridot.

Peridot is one of very few gemstones that is only found in one colour as it is idiochromatic, meaning that it is coloured by its chemical structure, in this case iron, and not by impurities. This contrasts with a gemstone like sapphire which is found in every colour of the rainbow coloured by elements like chromium for pink stones, or titanium/ iron for blue.

A vintage peridot ring from SHJB sold archives

It is the distinctive oily yellow-green colour of peridot that has captivated jewellery enthusiasts for centuries. Revered for its bright spring green peridot has been used to adorn us humans since it was first discovered c.1500BC. Originally mined on the island of Zabargad off Egypt, it is no surprise that the Egyptians history is littered with references to this stone, ‘the emerald of the night’. Some even suspect that Cleopatra’s famed emerald collection also contained a large number of these glowing stones.

St John's Island

Flashing forward centuries peridot is once again aligned with strong women when it became synonymous with the suffragette movement. The suffragettes well known for their colours: purple for royalty, white for purity and green for hope as the “emblem of spring”. It is no surprise that peridot was the perfect fit for the suffragettes, with powerful and rich members showing their allegiance to the movement with fine articles of jewellery in these revolutionary colours.

A fine Suffragette ring from the SHJB sold archives

There is no doubt the easiest way to identify peridot is by its unique colour, but there are also a few tell-tale signs hidden within the stone. The first is double refraction, peridot is a gemstone with a very high birefringence, this meaning that when light enters the gemstone the crystal structure forces it to split into two different light rays that move independently through the crystal, the distance between these two light rays is so great in peridot that you can actually see it with the naked eye, which results in everything inside the stone looking like it’s being doubled.

The second are diagnostic inclusions called lily pads, no named because of their striking resemblance to this common pond plant. These inclusions are usually formed with a small crystal inclusion to the centre, often black or brown in colour, with a small stress fracture radiating around it like a halo.

An example of lily pad inclusions and double refraction in a peridot

A truly unique gemstone and one we love to see in antique and vintage jewellery alike. Peridot is relatively low cost as a gemstone and makes it a great option if you are looking for a bright gemstone without a hefty price tag, although particularly fine examples can reach thousands of pounds.

1 commentaire

12 févr.

Very interesting, I have learnt new facts about Peridot, my Birthstone, thank you.

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