The 1924 Boucheron Harcourt diamond bandeau tiara sold for £508,400 ($682,146)BonhamsA 1924 Boucheron Harcourt diamond bandeau tiara with exceptional provenance was the top lot at Bonhams’ Exceptional Jewels auction in London on June 11. Appearing at auction for the first time since it was commissioned by Boucheron in London more than a century ago, the tiara sold for £508,400 ($682,146), far exceeding its estimate. The piece was acquired by Boucheron's Heritage Department for its private collection.“Inspired by classical antiquity, the tiara’s olive leaf motifs symbolize peace and prosperity,” said Jennifer Tonkin, Bonhams’ head of jewelry, U.K.The tiara was one of several period and antique jewels from six notable single-owner collections that performed strongly during the sale. Sapphires, emeralds and signed jewels were among the most sought-after categories.“The sale reflects robust global demand for rare jewels distinguished by exceptional provenance, authenticity, craftsmanship and historical significance,” Tonkin said.A diamond ring with a with a 25.48-carat unheated Sri Lankan sapphire fetched £432,200 ($579,900) BonhamsSapphires dominated the next three highest-selling lots. A diamond ring centered with a 25.48-carat unheated Sri Lankan sapphire fetched £432,200 ($579,900), nearly five times its high estimate.A diamond ring with a 5.63-carat Kashmir sugarloaf cabochon sapphire achieved £292,500 ($392,462)BonhamsPlay Puzzles & Games on ForbesA diamond ring featuring a 5.63-carat Kashmir sugarloaf cabochon sapphire of “Royal Blue” color achieved £292,500 ($392,462), more than double its high estimate.An Aldao diamond ring set with a 14.65-carat Burmese sapphire fetched £241,700 ($324,301)BonhamsAn Aldao diamond ring set with a 14.65-carat oval-shaped Burmese sapphire sold for £241,700 ($324,301), also more than double its high estimate.An emerald and diamond brooch, circa 1880, sold for £178,200 ($239,100)BonhamsEmerald jewels claimed the next three spots. Leading the group was a circa 1880 brooch depicting ivy leaves, set with diamonds and topped by three polished emerald beads suspended from rose-cut diamond surmounts. The brooch realized £178,200 ($239,100), more than five times its high estimate.A diamond ring with a 9.13-carat octagonal step-cut Colombian emerald fetched £178,200 ($239,100)BonhamsA diamond ring centered with a 9.13-carat octagonal step-cut Colombian emerald also sold for £178,200 ($239,100), more than triple its high estimate.Prevost emerald and diamond pendant earrings sold for £159,150 ($213,540)BonhamsA pair of Prevost diamond pendant earrings featuring pear-shaped Colombian emeralds weighing 15.29 and 15.76 carats sold for £159,150 ($213,540). The emeralds were framed by pavé-set brilliant-cut diamonds and suspended from brilliant- and oval-cut diamond surmounts.An Art Deco ruby and diamond necklace by the by Sterlé achieved £152,800 ($205,020)BonhamsAn Art Deco ruby and diamond necklace by the celebrated French jewelers Sterlé and Diringer, designed to convert into a pair of bracelets, achieved £152,800 ($205,020).A diamond ring centered with a 20.56-carat step-cut Colombian emerald also sold for £152,800 ($205,020).Aldao diamond bracelet and matching ear studs, which likewise achieved £152,800 ($205,020)BonhamsRounding out the top 10 lots was an Aldao diamond bracelet and matching ear studs, which likewise achieved £152,800 ($205,020).Other highlights included:Dame Nellie Melba’s Cartier Belle Époque seed pearl and diamond sautoir, circa 1910 sold for £127,400 ($170,940)BonhamsA Cartier Belle Époque seed pearl and diamond sautoir, circa 1910, from the personal collection of celebrated opera singer Dame Nellie Melba (1861–1931). The necklace features seed-pearl links accented with scroll and floral spacers millegrain-set with old brilliant, old single and rose-cut diamonds. A circular pendant with a radiating floral motif, similarly set with diamonds, completes the design. The sautoir sold for £127,400 ($170,940), far exceeding its high estimate.A diamond set wheatsheaf brooch, early 19th century, sold for £121,050 ($162,418)BonhamsAn early 19th-century diamond wheatsheaf brooch depicting four ears of wheat tied with a ribbon and set throughout with pear-, cushion- and rose-cut diamonds achieved £121,050 ($162,418), more than triple its high estimate.The Sidmouth portrait diamond jewel of Emperor Alexander I of Russia, circa 1810, realized £102,000 ($136,858). The jewel features a watercolor portrait miniature of Alexander I (1777–1825), Emperor of Russia from 1801 to 1825, wearing his military uniform and the breast star of the Imperial Russian Order of St. Andrew. The portrait sits beneath a portrait-cut diamond in a closed-back rose-cut diamond setting and is framed by a later surround of old brilliant- and old cushion-cut diamonds. Henry Addington, Viscount Sidmouth, helped arrange Alexander's visit to England in 1814, and the jewel is believed to have been presented to him as a diplomatic gift during that visit.A Cartier diamond, onyx and enamel bracelet, circa 1925, sold for £102,000 ($136,858)BonhamsA Cartier diamond, onyx and enamel bracelet, circa 1925, sold for £102,000 ($136,858). The articulated bracelet is set with old brilliant-cut diamonds and features a central curved plaque centered with a 5.82-carat brilliant-cut diamond. Millegrain detailing and black enamel terminals complete the design.