The Duchess was photographed wearing the stunning jewellery piece this week, and it is believed to be made from recycled materials.
It is designed by high-end jewellery designer Daniella Draper, and individual pendants are currently being sold at £1,270 a pop.
On Daniella's official website, the piece is described as shaped like "the moon" because: "the moon is universally representing the rhythm of time as it embodies the cycle. The phases of the moon symbolise immortality, eternity and enlightenment".
Each customer is able to have their pendant engraved with their initials or wording of choice, and a close-up look at Kate's reveals the initials 'G, C, L'.
A gift from her sister Pippa, it is similar to the W engraved charm she also gifted Kate, which of course symbolises her husband Prince William's initial.
The Duchess was shown wearing the stunning piece while launching a survey on childhood development.
Teaming the pendant with a simple black polo, she also wore a striking leopard print skirt, tan coat and boots.
At the launch of '5 big questions on the under 5s' in Cardiff, Wales, Kate opened up to fellow parents on some of the difficulties she faced as a new mother living in Wales while William worked night shifts.
She said: "I had a tiny tiny baby in the middle of Anglesey it was so isolated, so cut off. I didn’t have any family around and William was doing night shifts."
She also stressed the importance and meaning behind the groundbreaking survey: "The early years are more crucial for future health and happiness than any other moment in our lifetime.
"I want to hear the key issues affecting our families and communities so I can focus my work on where it is needed most."
The survey was commissioned by the Royal Foundation and aims to "spark the biggest ever conversation on early childhood".
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