Royal Tiaras Fit for a Queen

To celebrate her Diamond Jubilee, Queen Elizabeth II has allowed some of her prized jewels to be displayed at Buckingham Palace starting June 30, including the Diamond Diadem, originally created in 1821 for King George IV. A favorite of the Queen's, the stately crown features roses, thistles and shamrocks – the symbols of England, Scotland and Ireland.

The only British crown allowed to leave the country, the Imperial Crown was made for King George V for his trip to India to commemorate his coronation at the Delhi Durbar in 1911. Worn only once, the opulent crown features more than 6,000 diamonds and includes rubies, sapphires and emeralds.

Made in 1870 for Queen Victoria, the tiny crown stands about 3 inches tall and was designed to be worn atop the mourning veil she donned following the death of her beloved husband, Prince Albert.

Considered a favorite of the Queen Mum, the Boucheron was passed down from the estate of society hostess the Hon. Mrs. Greville, and later bequeathed to Queen Elizabeth II following the death of her mother in 2002. The tiara is often borrowed by Camilla, Duchess of Cornwall, who has taken to wearing it to state events.

Worn by monarchs at the end of the coronation ceremony, the Imperial Crown boasts some of the most famous stones in the world, including the Second Star of Africa diamond and the Black Prince's Ruby. The pearls suspended along the arches are thought to come from a pair of earrings once belonging to Queen Elizabeth I.

Kate Middleton opted for "something borrowed" when it came time to pick her wedding day headpiece – a 1936 Cartier halo tiara owned by Queen Elizabeth. Originally purchased by King George VI for the Queen Mother, the tiara was given to the Queen on her 18th birthday, and in turn, loaned to the bride for her April 29 nuptials.

Though Kate didn't wind up wearing any of these glittering contenders for her wedding – (from left) the Duchess of Teck, the Strathmore and the Delhi Durbar – her step-mother-in-law, Camilla, borrowed one from Her Majesty for a state banquet not long after her marriage to Prince Charles.

The Queen mum sported this simple yet stunning floral headpiece in 1928, a gift from her parents on the occasion of her marriage to Prince Albert two years earlier.

Queen Elizabeth gave this pearl-and-diamond tiara (seen on her in 1958) to Diana as a wedding gift, but experts tell PEOPLE they'd be surprised if the tiara will pass down to Kate.

This neoclassical crown once belonged to Queen Mary's mother, the Duchess of Teck, whose prized jewelry collection was passed down to her daughter upon her death in 1897.

A fortuitous move by the royal family or foreshadowing? Sarah Ferguson's diamond tiara did not come from the royal collection – but was purchased for her from Garrard's, the crown jewelers of the time, for her July 23, 1986, wedding to Prince Andrew.

Kate won't get the Spencer family headpiece that Diana wore on her wedding day. But she might land the sapphire necklace William's late mum got as a wedding gift from the Saudi Crown Prince, which she wore along with her tiara during an official tour of Australia in 1983.

Worn by Queen Mary (left), it was passed to granddaughter Elizabeth (right) on her wedding day. Since then, the regal headpiece has been spotted on the Queen during her visit to Bangladesh in 1983 and, more recently, to a state dinner in Toronto.

The Countess of Wessex Sophie Rhys-Jones wore a stunning yet modest tiara when she wed Queen Elizabeth's youngest son Prince Edward on June 19, 1999. The tiara, a wedding gift from the royal family, is believed to be made up of jewels once belonging to Queen Victoria.

Elizabeth loaned her mother's tiara to sister Princess Margaret for a state banquet at Buckingham Palace in 1954. Nearly 20 years later, her daughter Princess Anne donned the elegant headpiece during a royal tour of Australia and New Zealand in 1970.