Billie Eilish marks Grammy win with diamonds

Billie Eilish has marked her record-breaking Grammy Awards win with black diamonds.

The 18-year-old singer became the youngest artist, and only the second artist ever, to scoop the ceremony's four biggest categories - Record of the Year, Song of the Year, Album of the Year and Best New Artist - as well as Best New Artist in January, and she's commemorated the milestone with some new jewellery.

According to TMZ, Billie had a custom pendant made by celebrity jeweller Boodaddy Diamonds of Koosh Jeweler and the 14-carat gold chain features a large '5X' studded with black diamonds, to mark her five award wins.

It's unknown how much the jewellery cost, but similar pieces have previously sold for around $30,000.

The 'Bad Guy' hitmaker's brother Finneas O'Connell - who produced Billie's award-winning album 'When We All Fall Asleep, Where Do We Go?', and also won Producer of the Year at the Grammies - previously admitted the pair were "embarrassed" to have had such a successful night at the ceremony.

He said: "[Billie] was very grateful, obviously, and a lot of her friends were there. She has more 'go with the flow' than I do, but we were both kind of embarrassed to win so much; you hope that it will be kind of equal but after the third in a row ... well, we love all of our fellow nominees."

The duo were convinced they wouldn't be taking home any of the big accolades on the night, and Finneas says he was rooting for Lizzo and Lil Nas X.

He added: "If I'd bet on anyone, I would have lost money in us winning everything. I thought 'Truth Hurts' would win record of the year. And I thought 'Old Town Road' would win song of the year, because it was. I was hopeful about album of the year, and that's one that I'm really proud of, because I love listening to that album front to back. That was the only one that I was like, 'Maybe!'"