Congratulations, Beth! The description certainly fits the tiara worn by Lady Rose.

Lady Rose's mother-in-law, Castila (in some sources: Castalia) Rosalind, Dowager Countess Granville, owned a very unique second tiara which is now – together with its accompanying necklace and earrings – in the collection of the British Museum.

»In 1884, Lord Granville (George Leveson-Gower, 2nd Earl Granville, 1815–91), as Foreign Secretary, concluded the Anglo-Portuguese trade treaty regarding the Congo River basin. According to family tradition, the Portuguese ambassador wished to mark the treaty by presenting a piece of beetle jewellery to Lady Granville (Castalia Rosalind, Countess Granville, 1847–1938). Lord Granville refused this offer, presumably fearing it could be seen as bribery, but permitted his wife to accept the beetles, which he then had mounted for her. He chose the London jewellers Phillips Brothers & Son, known for their recreations of historic jewels and archaeological discoveries.«

Parure of tiara, necklace and earrings formed of dried South American weevils (lamprocyphus augustus) with iridescent green wing cases, mounted in gold in the Egyptian taste with lotus motifs. On the necklace and earrings, the lotuses are interspersed with tiny gold rods ending in black enamel beads.

Images © The Trustees of the British Museum