The Cullinan....
The Cullinan...Gonna be More Expensive Than Kohi-Noor..
Also Known As The Star of Africa. 530.20 carats.
(The stone can be removed from the Royal Scepter and worn as a pin or pendant.)
The Star of Africa, a pear shaped diamond weighing 530.20 carats, aka the Cullinan I. It measures 58.9 × 45.4 × 27.7 mm, and has 76 facets (counting the culet and the table). It is called the Cullinan I because it's the largest of the 9 large stones cut from the Cullinan Diamond, and the Cullinan II is the massive 317.40-carat cushion shaped diamond in the center-front of the Imperial State Crown of Great Britain. The Crown also features the Black Prince's Ruby, as well as St. Edward's Sapphire, and the Stuart Sapphire. All the stones in the crown seem to have a history. The Star of Africa holds the place of 2nd largest cut diamond in the world and is on display with the other Crown Jewels in the Tower of London.
The nine largest pieces of the Cullinan Diamond. The largest piece would of course be cut into the Cullinan I (530.20 carats)
and the the next largest into the Cullinan II (317.40 carats), and so on. This photo was probably taken in 1908, the year
after the Cullinan rough was presented to King Edward VII for his 66th birthday. 
Publicity photo of the Cullinan crystal being handed from Fred Wells (right)
to McHardy, who then hands it to Sir Thomas Cullinan (left).
Late one afternoon in 1905, Mr. Frederick Wells, the superintendent of the prolific Premier Mine in South Africa, was making a routine inspection trip through the mine when his attention was attracted by something reflecting the last slanting rays of the setting sun. Curious, he stopped for a closer look. He was eighteen feet below the surface of the earth, and the shiny object was on the steep wall of the mine a few feet above him. Mr. Wells quickly scaled the wall and extracted from the blueground what appeared to be a large diamond crystal. At first, he thought he was being fooled by a large piece of glass, but tests proved it to be the largest gem-quality diamond ever discovered. It weighed 3106 carats, or about 1⅓ pounds. It was named after Sir Thomas Cullinan, who opened the mine and was visiting on that eventful day. Many diamond experts believe that the huge stone was only a fragment, and that another piece, (possibly as large or even larger) either still exists and awaits discovery, or was crushed in the mining process. The latter is very unlikely. The prospect of finding the portion of the Cullinan has added zest to the activities of numerous miners and prospectors. The Cullinan was sold to the Transvaal government, which presented it to King Edward VII on his 66th birthday on November 9th, 1907. It was insured for $1,250,000 when it was sent to England. The King entrusted the cutting of the stone to the famous Asscher's Diamond Co. in Amsterdam, which had cut the Excelsior and other large gems. The huge diamond was studied for months. On February 10th, 1908, Mr. Asscher placed the steel cleaver's blade in a previously prepared V-shaped groove and tapped it once with a heavy steel rod. The blade broke, but the diamond remained intact! The second time, it fell apart exactly as planned, and an employee at the factory reported that Mr. Asscher had fainted. A second cleavage in the same direction produced three principal sections; these in turn would produce nine major gems, 96 smaller brilliants, and 9.50 carats of unpolished pieces. The nine larger stones remain either in the British Crown Jewels or in the personal possession of the Royal Family. These historically celebrated gems and their present mountings are as follows: The Cullinan I, also known as the Star of Africa, weighs 530.20 carats. King Edward placed it in the Sovereign's Royal Sceptre as part of the Crown Jewels, and it is now on display in the tower of London. The Cullinan II is a 317.40 carat cushion cut stone mounted in the band of the Imperial State Crown, it is also in the Tower of London as part of the Crown Jewels. The Cullinan III is a pear-shaped diamond weighing 94.40 carats, and is in the finial of Queen Mary's Crown and can be worn with the IV as a pendant-brooch. Many of Queen Mary's portraits show her wearing these two stones, and Elizabeth II makes use of them the same way. The Cullinan IV, a 63.60-carat cushion shape, was originally set in the band of Queen Mary's crown, but can also be worn as jewelry, as described above. The Cullinan V is a triangular-pear cut weighing 18.80 carats, was originally mounted in a brooch for Queen Mary, to be worn alternately in the circlet of her crown as a replacement for the Koh-i-Noor. This was after the Koh-i-Noor was removed to the new crown that was made for Elizabeth (now the Queen Mother) in 1937.
The Cullinan IV (upper, 63.60 carats) and Cullinan III
(lower, 94.40 carats), set in a pendant brooch. The Cullinan VI, an 11.50 carat marquise-cut stone, was originally presented by King Edward to his wife, Queen Alexandra, and is now worn by Elizabeth II as a drop on a diamond and emerald necklace. It was worn more frequently by the young Queen than any other section of the Cullinan. The Cullinan VII is an 8.80 carat marquise-cut stone mounted in a pendant on a small all-diamond brooch, in the center of which is the 6.80-carat cushion cut Cullinan VIII, and lastly, the Cullinan IX, a 4.39 carat pear shape, is mounted in a ring with a prong setting that was made for Queen Mary; it too is sometimes worn by Queen Elizabeth.
The Cullinan VI (lower, 8.80 carats) and Cullinan VIII (upper, 6.80 carats)
Elizabeth II's Imperial State Crown of Great Britain Imperial State Crown: originally made for Queen Victoria's coronation in 1838, it was remade for George VI in 1937. It contains the 317.40 carat Cullinan II. The large stone above the Cullinan II is the Black Prince's Ruby, which is actually a red spinel. The stone was at one time a giant bead. Note the red dot on the upper part of the stone - that is a ruby that was used to plug a small hole that went right through the stone. The Stuart Sapphire is a very fine 104-carat oval shaped sapphire that appears on the backside of the crown. It was amoung the Crown Jewels of Charles II. The sapphire in the center of the cross on the top of the crown is St. Edward's Sapphire, (believed to have belonged to Edward the Confessor), and the four large drop-shaped pearls are said to have been Elizabeth I's earrings.
The Cullinan II Diamond. Note the two tiny platinum loops on the edges.
This is so the stone can be worn as a brooch, alone or with the Cullinan I
attached. However, it usually resides in the front of the Imperial State Crown.
St. Edward's Sapphire, from the top of the Imperial State Crown. Photo © HMSO, London 
The Black Prince's Ruby on the front of the Imperial State Crown, a name which is misleading because the stone is actually a red spinel weighing about 170 carats. The gem is a large bead - the lighter-colored dot on the front of the stone is actually a ruby plugging up the hole that goes through the stone. Photo © HMSO, London.