GENEVA: A tiara passed down through generations of Italy's royal family will be among the highlights at a Sotheby's auction of jewels in Geneva next week.

Dating to the second half of the 19th century, the tiara was a wedding gift to Maria Vittoria dal Pozzo upon her marriage in 1867 to Amadeo I of Savoy, later king of Spain.

The tiara features graduated scroll motifs set with diamonds and natural pearls and is on sale with an estimate price of $1 million to $1.5 million.

"It's a true, beautiful and historic piece which has remained in the House of Savoy for over 150 years," said Benoit Repellin, head of magnificent jewels sales at Sotheby's.

The May 11 sale also features large diamonds and coloured gemstones, including a 1930s sapphire and diamond brooch featuring the largest Kashmir sapphire ever to appear at auction - a 55.19-carat oval gem - alongside a Kashmir sapphire weighing 25.97 carats.

Estimated to fetch $2 million to $3 million, it belonged to an heiress of the Guinness brewery fortune, said Olivier Wagner, senior director of the jewellery department at Sotheby's.

Kashmir sapphires are sought after as they were discovered at the end of the 19th century and the mines were only exploited over 20 years, he told Reuters.

"The only way to find them is to buy them at auction," he said.