The 'Diamonds' singer is said to have purchased the jewellery using her own funds as her management were not sure about the idea.
"She's been offering to pay for the diamonds out of her own pocket because management weren't keen," a source told The Sun.
"She just wants everyone who goes to the gigs to be totally overwhelmed."
The Bajan star is also rumoured to have ordered a diamond-encrusted microphone and mic stand for the shows, which begin in Buffalo, New York on March 8, 2013.
Rihanna's new album Unapologetic is released on November 19 in the UK and the day after in the US.
The singer was recently named the second biggest selling female solo artist in UK chart history by The Official Charts Company.
Watch the lyric video for Rihanna's 'Diamonds' below: