The Amethyst Necklace Tiara from Norway's royal collection couldn't be simpler to sort out: it's a tiara of amethysts that is convertible to a necklace. The amethysts are surrounded by diamonds and are supported by small diamond flowers in this petite piece, which is actually part of a parure.
This is another tiara which is said to have been a gift from King Harald to his wife, Queen Sonja (that makes two now - and whether you like his taste or not, you have to give the guy credit for adding to the family collection!). Sonja wore it as both a necklace and a tiara before handing it over to her daughter-in-law, Crown Princess Mette-Marit. Mette-Marit was first spotted in the tiara during the pre-wedding celebrations for Crown Prince Frederik and Crown Princess Mary of Denmark in May 2004. Considering that Mette-Marit had just given birth to heir to the throne Princess Ingrid Alexandra a few months before, many have wondered if this was a post-baby present.
Crown Princess Mette-Marit
Though she seems to maintain her Diamond Daisy Tiara as her favorite, Mette-Marit makes good use of this set. In addition to the tiara converting to a necklace (which we haven't seen Mette-Marit do yet), there is a set of earrings, a brooch which can be worn as a necklace pendant, and a simpler necklace that can break down into two bracelets.
Princess Märtha Louise
The tiara gained a third wearer in 2010, when Princess Märtha Louise wore it for Crown Princess Victoria of Sweden's wedding. She did what I think you must do to make this a successful piece: she backed it up with some serious hair. Because the unfortunate thing with this tiara is that it suffers from the same ailment that many necklace tiaras do, which is sparseness. That said, there are woefully few amethyst tiaras lurking about in royal houses, and this purple lover will cheer them on whenever possible.