The couple confirmed their engagement recently and Christian made it official with a stunning $400,000 (about R6 million) diamond sparkler, surrounded by smaller jewels.
Andrew Brown, President of WP Diamonds, told E! News: "Lady Gaga's spectacular ring appears to be a 6-7 carat pink sapphire with a diamond halo totaling 3-4 carats. This is likely a high quality, no heat treatment, pink sapphire. It looks like it may be a Padparadscha sapphire, in which case this ring would easily retail between $300,000 and $400,000."
Lady Gaga confirmed her engagement as she was honoured at the Women In Hollywood Awards, hosted by Elle magazine in Beverly Hills, where she referred to her love as "my fiancé".
And in her documentary, 'Gaga: Five Foot Two', the star explained that she often asks Christian, as well as the other members of her family, for advice when it comes to her career.
She said: "It's not just about it being my boyfriend. I ask that of many people in my life, and my family, all the time. At the end of the day, I'm my father's daughter, my mother's daughter, my sister's sister."