It’s a huge amethyst and diamond parure. Comprised, a collection of generously sized amethysts, primarily oval and framed by diamonds.

Part of the parure:
an Amethyst Tiara, circa 1815, of Empire style, the tapered band set with cushion-shaped amethyst bordered by similarly shaped diamonds, later fittings and several repairs;The tiara includes large oval amethysts positioned vertically between sets of two horizontally stacked smaller oval amethysts. The whole diadem is studded with extra diamonds and is enclosed by a straight row of diamonds at the top and bottom. Though rounded gems of any sort surrounded by diamonds is an old concept like an kokoshnik.

an Amethyst Necklace, circa 1815, designed as a row of ten oval amethysts graduated in size from the front and each bordered by cushion-shaped diamonds and connected by diamond quatrefoil motifs, the front supporting detachable pear-shaped amethyst drops, four of which are briolette, all of the clusters are detachable;

an pair of Earrings with Amethyst and Diamonds of similar design, early 19th Century;

and an Amethyst and Diamond Ring, last quarter of the 19th Century, slightly imperfect"

The tiara, necklace and earrings are circa 1815, and the ring is late 19th century, Offered by Sotheby’s Geneva, May 1993, est $75,000-125,000.

According to some notes in 1993 , after the tabloid press claimed that the Queen Mum was selling this suite, Buckingham Palace asked Leslie Field to deny the story, which she did.
The suite was sold in Geneva in 1993 for £55,357 but it is not known who the seller was. Later that year the suite appeared on view at the London Grosvenor House Antiques Fair for sale at £150,000.

 

The centre is the table of the large amethyst and the "arms" that radiate out are the edges of the facets, which creates the sense of something hanging, but in fact is the central amethyst.

Queen Mary wore the amethyst tiara till her death, a picture was taken, when she visit the royal ballett in the 50th, wearing the tiara.

In the picture above she wore an large amethyst brooch with an frame of fine scrollwork of diamonds, as devante de corsage, with one of the pendants of the earrings. Probably one of her wedding gifts of 1893, which is noted as present from M Burdett-Coutts.

 

Russia: Royalty & the Romanovs The Imperial Amethyst and Diamond Brooch made by Faberge, will be on display at The Queen’s Gallery, Buckingham Palace 9 November 2018 – 28 April 2019.

Sources: Royal Collection;Life Magazin;Sothebys