At 'white-tie' occasions a tiara is no longer required. However, tiaras are still being made and some auction houses and jewellers are seeing an increased interest in tiaras since the beginning of the 21st century. Fashion designer Versace made a tiara which was worn by pop star Madonna. The Danish royal family has a tiara on loan that was designed in 2009 for an exhibition of classic and modern tiaras. Collections Queen Elizabeth II is said to have had the largest and most valuable collection of tiaras in the world, many of which are heirlooms of the British royal family. She was often seen wearing them on state occasions. The Queen inherited many of them, especially from Queen Alexandra. She also inherited a number of tiaras designed by Prince Albert for Queen Victoria. Queen Mary purchased the Grand Duchess Vladimir tiara in the 1920s. It consists of numerous interlocking diamond circles. Pearl drops or emeralds can be attached inside the circles. Queen Mary had a tiara made for the Delhi Durbar held in 1911 in India. It is now on loan for wearing by Camilla, Queen Consort of the United Kingdom, wife of King Charles III. Queen Elizabeth II commissioned a ruby and diamond tiara. A gift of aquamarines she received as a present from the people of Brazil were added to diamonds to make a new tiara. Other queens, empresses, and princesses regularly wear tiaras at formal evening occasions. The Swedish Royal Family have a collection as do the Danish, the Dutch, and Spanish monarchies. Many of the Danish royal jewels originally came into the collection when Princess Louise of Sweden married the future King Frederick VIII of Denmark. The Romanov dynasty had a collection up until the revolution of 1917. The Iranian royal family also had a large collection of tiaras. Since the Iranian Revolution, they are housed at the National Jewelry Museum in Tehran. On rare occasions, usually when the actual tiara is exceptionally old and valuable due to its history and gemstones, realistic copies may be made and worn in place of the original due to insurance considerations. Costume jewellery tiaras Tiaras made of plastic, rhinestones, Swarovski crystals, or any other non-precious material are considered costume jewelry. They are worn by women on special occasions such as homecoming or prom and at their quinceañera (fifteenth birthday) or wedding. They are also worn by the winners of