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The Stunning Star Sapphire Explained

Aug. 18 2014
There are so many options for sapphire engagement rings. The star sapphire is a rather unique and rare alternative to the norm.

Chatting to K over pizza and wine last night, I told her we were considering looking into sapphire engagement rings. I knew she would approve as the unconventional side of her loves the idea of anything other than a diamond as a central stone. She got very excited and asked me if I was considering a star sapphire.

I was a little embarrassed to say that this was another one I had not heard of, and she took great pleasure in explaining to me the concept of the star sapphire.

What is a Star Sapphire?

These stunning stones can occur in every colour of sapphire, although yellow, orange and green star sapphires are uncommon. They are given their name because of the optical phenomenon caused by their shimmering rays that create a sparkle like no other.

This work is a derivative of "Star of India Sapphire Cabochon" (http://goo.gl/5OhGRk) by Jill Clardy (http://goo.gl/PpkDDB)), used under CC BY 4.0. "Star of India Sapphire Cabochon" is licensed under CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/) by F&L Designer Guides

This work is a derivative of “Star of India Sapphire Cabochon” (http://goo.gl/5OhGRk) by Jill Clardy (http://goo.gl/PpkDDB), used under CC BY 4.0. “Star of India Sapphire Cabochon” is licensed under CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/) by F&L Designer Guides

Known as ‘asterism’, from the Latin word astrum for ‘star’, this phenomenon is actually caused by the needle-like inclusions of a mineral known as rutile.

Are These Sapphires Transparent?

The issue of clarity in star sapphire engagement rings is complex and although the ideal stone would be transparent, the rutile infiltrations that cause the optical phenomenon also appear as inclusions. A fine sapphire has to have enough silk inclusions caused by the rutile to create a well-defined and bright star without affecting the transparency of the gem. K went on to explain that translucent to semi-transparent stones are the best. This is because colour saturation decreases as opacity increases, so a bright well-defined star on a sapphire may equal a dull overall appearance.

What about the Cut?

K seemed to be well informed about these star sapphires and I guessed it was because they appealed to her rather girly, romantic side. I loved that about her and the more she made me think outside my comfort zone the more I was intrigued. I went on to ask her if she knew anything about the best cut for star sapphire engagement rings and of course she did.

The star has a big impact on the cut of star sapphires, as its definition and orientation is the stone’s prime feature.

K explained how the star should be centred when viewed from above and that each ray should be equal in length. You want sharp rays that exude brightness and clarity and reach from the crown to the base with seamless precision. Absolute perfection though can be a sign of a man-made star sapphire so you do have to be wary when purchasing one.

Treated or Untreated?

When I got home I decided to look into star sapphire engagement rings further and wasn’t surprised to hear that many are today treated to increase their beauty, as are for example rubies. F pointed out too that the more stones out there that are treated, the harder it would be find original fine star sapphires. He had a point but I still want to keep the possibility of having a unique and stunningly beautiful star sapphire under my hat.


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