A 12.55 carats Colombian emerald and diamond brooch, circa 1965. Estimate £120,000 - 180,000 (€160,000 - 250,000). Photo: Bonhams.

The octagonal step-cut emerald, weighing 12.55 carats, in a four double-claw setting within a baguette-cut diamond spray surround, diamonds approximately 2.50 carats total, diameter 3.2cm

Accompanied by a report from SSEF stating that the emerald is of Colombian origin, with no indications of clarity enhancement. Report number 78391, dated 17 February 2015.

Accompanied by an appendix letter from SSEF stating that a natural emerald from Colombia of this size and quality is rare and exceptional and merits special mention and appreciation. The emerald demonstrates hallmarks of Colombian emeralds from the famous mining areas of Muzo, Coscuez and Chivor.

A 2.65 carats Colombian emerald and diamond dress ring, circa 1965. Estimate £8,000 - 10,000 (€11,000 - 14,000). Photo: Bonhams.

The cut-cornered step-cut emerald, weighing 2.65 carats, within a starburst surround of tapered baguette-cut diamonds, ring size O (sizing band)

Accompanied by a report from Gübelin stating that the emerald is of Colombian original, with indications of minor clarity enhancement. Report number 15030054, dated 9 March 2015.

BONHAM'S. FINE JEWELLERY, 22 Apr 2015 14:00 BST -LONDON, NEW BOND STREET