Tallulah Willis shared photos of her giant engagement ring, and an expert says it could be worth up to $200,000

• Tallulah Willis, the 27-year-old daughter of Demi Moore and Bruce Willis, is engaged.
• She shared photos of her fiancé Dillon Buss proposing, and close-up shots of her engagement ring.
• Ajay Anand of Rare Carat told Insider that her 1910s-era ring could have cost up to $200,000.

Tallulah Willis, the youngest daughter of Demi Moore and Bruce Willis, is engaged to film director Dillon Buss.

The couple announced the news via Instagram on Tuesday, and shared numerous photos from their proposal - including the first shots of the 27-year-old's giant engagement ring.

According to Ajay Anand, the founder and CEO of diamond search engine Rare Carat, Willis' ring could have cost around $200,000.

In an Instagram post, Willis said she "had to be in the drivers seat" when it came to choosing her ring due to her "lowkey (highkey lol) obsessive, perfectionist, micro-lens way of viewing special things" in her life.

She also described her fiancé as "the most understanding precious human noodle," and said that he understood why she wanted to take the lead once they began "seriously" discussing an engagement.

From there, according to Willis, she and a friend "scoured the world" and left "no stone unexamined."

"After much deliberation we decided on this 1910s elongated asscher cut forged in a riverbed," she wrote.

A post shared by tallulah (@buuski)

Speaking with Insider over email, Anand said Willis' step-cut jewel - which is a rectangle shape - looks like it is between a 5- or 6-carat diamond.

"Step-cut diamonds like this one require high clarity, so you can be assured this is a very clean stone," he said. "Paris Hilton and Bethenny Frankel also picked step cuts for their recent engagements. The cut is classic and on-trend."

Her band, according to Anand, appears to be "sleek" and "tapered." He believes it's made from 18-karat gold, as 14-karat gold would look "less bright-yellow in tone."

"Yellow hues are complemented by yellow gold, making it likely that the designer went down to a lower color to compensate for the cost of a high clarity diamond," he continued. "It's a smart way to save cash if your heart's not set on platinum."

Anand added: "All told, It is a very unique cut. This one would cost a ton more if it was set in platinum, requiring a D, E, or F colorless diamond."

A post shared by tallulah (@buuski)

Before talking about her engagement ring online, Willis first shared pictures of Buss proposing to her in what appears to be a backyard. For the post's caption, she wrote: "with absolute most certainty."

A post shared by tallulah (@buuski)

Buss, on the other hand, shared his own series of pictures and wrote: "I can finally call you my fiancée. Love you forever Buuski Lu, you are my best friend ❤️ #maythefourthbewithus."

A post shared by (@dillonbuss)