I do think that Queen Mary was wearing the amethyst brooch given as a wedding gift from William Burdett Coutts with a pendant from the parure.
The amethyst has the same shape and the diamond border seems to match.
Queen Mary reportedly gave the parure to the Queen Mother, but it was later sold at auction. It is wrong and wrong
The truth : Queen Mary gave the parure (certainly in her will) to Princess Margaret in 1953. (Certainly she wanted her granddaughter having a parure like her daughters-in-law.)
Princess Margaret appeared to have no affection for this stone as she had never worn it in public.
Princess Margaret sold this parure in 1982 (she need money...).
A man posted photos of this parure worn by his former wife on a public blog. I have sent a private message. He kindly answsered me. I asked him many questions and I answered me . He also sent me private photos of his wife wearing the very beautiful parure !
As Beth has written I find also interesting that Queen Mary never gave the amethysts to any of her daughters-in-law ; she kept the jewels and continued to wear them. If she had a special affection to this stone she could have bequeathed it to QEII in order to this parure remain in the main branch.
From the sell :
"Part of the parure:
1. 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.
2. 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;
3. an pair of Earrings with Amethyst and Diamonds of similar design, early 19th Century;
4. An Amethyst and Diamond Ring, last quarter of the 19th Century, slightly imperfect""
From Royal Magazin :
"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."
In recent years, Vogue editor Anna Wintour has been photographed wearing the necklace from the set.
The image is one that I posted on the RJWMB some years ago. It shows Princess Xenia with Queen Mary in 1937.
Throughout the late 1920s, the 1930s and the 1940s Queen Mary appears to have worn her amethysts frequently. What I find interesting about the reports is that HM definitely was not wearing mourning or half mourning dress.
I have never done a full search, but on at least two occasions during the 1930s Queen Mary was reported to have worn an amethyst tiara and brooches for formal Courts. Again, there is no sign that the royal ladies were in mourning and, on one occasion, Queen Mary was reported to have worn a heavily beaded white gown.
While George V reigned, I find it is impossible to ascertain from the descriptions whether Queen Mary wore the Kent amethyst brooch or her own amethyst brooches. From 1937 the brooches would have been her own.
One of these can be seen in the image below from 1893.
It is possible that the same brooch can be partially seen from this 1939 occasion.
Another that we have an image for is the amethyst brooch given to Queen Mary as a wedding gift from William Burdett Coutts
The latest photo I have of Queen Mary wearing the tiara is from 1949.
I find it interesting that Queen Mary never gave the amethysts to any of her daughters-in-law; she kept the jewels and continued to wear them.
Franck was the one who eventually discovered what had happened to the amethysts, so I'll let him explain.