Lily Collins' unique engagement ring is puzzling gemologists, who say it could be worth anywhere from $5,000 to $100,000

• Lily Collins announced her engagement to the film director Charlie McDowell on Friday.
• Collins confirmed the news on Instagram, sharing photos of the proposal and a close-up shot of her engagement ring.
• Collins' ring features a see-through square stone set inside a thick yellow-gold band.
• According to Ajay Anand, the founder and CEO of the diamond search engine Rare Carat, the ring could feature a diamond or quartz.
• If it's quartz, Anand said it was likely to have cost under $5,000, but if it's a diamond, it could be worth up to $100,000.

Lily Collins is engaged to the film director Charlie McDowell.

The "Emily in Paris" star celebrated the milestone on Friday with an Instagram post in which she shared the first close-up photo of her engagement ring. She wore a unique square-shaped stone set inside a thick yellow-gold band, which perfectly matches other jewelry Collins is seen wearing in the photo.

According to Ajay Anand, the founder and CEO of the diamond search engine Rare Carat, Collins' engagement ring could have cost anywhere between a couple thousand dollars and $100,000.

In an email sent to Insider, Anand said the unique ring "generated a heated debate" between gemologists at Rare Carat.

"First, this is a nontraditional engagement ring — an unusual choice for a celebrity," Anand said. "It's a cushion-shaped stone in a yellow-gold bezel setting, with an open-back cut so you can see through to the skin."

Anand added that his team would need "a closer look" to determine whether the stone in Collins' ring is a diamond or gem.

"If it is a diamond, it's a rare flatter cut and in the four-carat range — putting the retail value between $50,000 to $100,000," he said. "If it isn't a diamond, it's likely a quartz, which would cost less than $5,000."

While it's unclear how long Collins and McDowell have been dating, they first hinted at their relationship on Instagram in August 2019.

About one year later, they are engaged. In her Instagram post, Collins shared an image taken as McDowell proposed to her and another in which she's seen holding her ring up and kissing her fiancé.

"I've been waiting my lifetime for you and I can't wait to spend our lifetime together," Collins wrote alongside the photos.

In July, Collins celebrated her now-fiancé's birthday with a touching note on Instagram. She also included a photo of them embracing in a forest.

"Today it's your birthday and yet I feel like I'm the lucky one," Collins wrote. "You're a true gift of a human @charliemcdowell. An incredible boyfriend and the best dog dad to @redforddog. You've opened my eyes and deepened my heart."

Collins added: "You constantly inspire me to dream big and go outside of my comfort zone. Every day is an adventure with you and I can't wait to explore more of the world together (when we can). I love you so much."

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