Greek soprano Maria Callas is best remembered for her role as Tosca

An 11.7 carat marquise-shaped diamond ring is the most expensive of the pieces Sotheby's hopes to sell, and should fetch up to �100,000.

Eleven pieces given to the singer by her husband, the wealthy industrialist Giovanni Battista Meneghini, will be part of the November sale in Geneva.

Callas left the jewels to a friend when she died in 1977.

The current owner-turned-seller's identity has not been revealed.

Acclaimed role

Also in the lot will be a chunky emerald and diamond ring, valued at between �45-78,000, and a ruby and diamond Van Cleef and Arpels brooch expected to fetch �28-45,000.

Callas, famed for her acclaimed role as Tosca in Franco Zeffirelli's stage production of the Puccini opera, married the Italian Meneghini in 1949.

She later left him for Greek shipping magnate Aristotle Onassis. They shared a stormy relationship until he wed Jacqueline Kennedy in 1968.