The Australian billionaire, who started dating the 45-year-old singer after meeting her after one of her Las Vegas concerts in May, reportedly presented her with a 18-carat heart-shaped yellow diamond on a platinum chain before she went on stage at Caesars Palace on Wednesday night (22.07.15).
A source told gossip website TMZ.com that the star dedicated her hit 'Hero' to her 47-year-old beau to show her gratitude after he surprised her with the generous gift.
Before launching into the song, the '#Beautiful' hitmaker, who split from estranged husband Nick Cannon last summer after six years of marriage, told the audience: 'I have a new heart. James is in the house tonight.''
It was previously reported James is eager to marry Mariah as soon as her divorce from Nick, 34, is finalised.
A source said: ''James wants to marry her sooner rather than later, and she is very open to the idea.''
And the couple are said to have already discussed having a child together, as Mariah, who has four-year-old twins Moroccan and Monroe with Nick, wants to have another baby with James, who has three children from previous relationships.
Another insider said: ''Mariah feels that having a child with James would be a blessing from God.
''She wants another child and is telling friends she's not too old.''
The biggest names in music royalty.