Whilst Shannon Delany-Ron, Director of Communications at JamesAllen.com, added: "Three-stone rings like Demi's hold symbolic meaning and represent the past, present and future of a relationship.
"Beauty and precision are hallmarks of emerald-cut diamonds. This timeless style is a popular choice for engagement rings. Meghan Markle wears a similar three-stone ring and Jennifer Lopez, Amal Clooney and Jennifer Lawrence all have said 'yes' to emerald-cut engagement rings."
Demi announced her engagement to the 'Young and the Restless' actor - who she first started dating in March - in a sweet post on Instagram.
Alongside a series of snaps showing off her engagement ring, she wrote: "When I was a little girl, my birth dad always called me his 'little partner' - something that might've sounded strange without his southern cowboy like accent. To me it made perfect sense. And today that word makes perfect sense again but today I'm officially going to be someone else's partner ...
"@maxehrich – I knew I loved you the moment I met you. It was something I can't describe to anyone who hasn't experienced it firsthand but luckily you did too.. I've never felt so unconditionally loved by someone in my life (other than my parents) flaws and all."
"You never pressure me to be anything other than myself. And you make me want to be the best version of myself. I'm honoured to accept your hand in marriage."
"I love you more than a caption could express but I'm ecstatic to start a family and life with you. I love you forever my baby. My partner. Here's to our future!!!! (sic)"