Cochise College               Student Papers in Geology  
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Roger Weller, geology instructor

Sheila DeMeritt

Physical Geology
Spring 2005

The Cullinan Diamonds

            Diamonds are a part of geological history.  The youngest volcanic rock in which diamonds have been found is about seventy million years old.  The diamond is rated ten on the Mohs scale of hardness.  Its hardness surpasses any other substance found in nature.  The rough diamonds occur in a variety of shapes, octahedra, dodecahedra, twinned octahedral and broken or cleavage fragments.

            Throughout history diamonds have been a source of romance and mystery, a symbol of wealth, power and legend.  The brilliant beauty of a diamond is brought out by an exquisite cut.  A perfectly cut and faceted diamond comes to life with a fire all its own.

            For centuries diamonds have been sought after and mined all over the world.  Stories of bad luck or curses were made up by powerful men to ensure the safety of their beautiful gems.  These stories are intriguing and have drawn a great deal of attention to these gorgeous stones.

            One of the more famous diamonds is the extremely large Cullinan Diamond.  It is the world’s largest gem quality diamond weighing 3,106 carats, the equivalent of one and a half pounds.  This diamond came from the Premier Mine in South Africa and was found in 1905.  A mine superintendent named Frederick Wells discovered the stone.  At first, he thought some of the miners had placed a piece of glass on the edge of the mine pit as a joke.  When he realized there was no one else around, he pried the diamond loose.  This rough diamond had a cleavage face, and experts thought that it was only a piece of a much larger diamond (World’s Most Famous Diamonds).  The huge diamond was named Cullinan after the mine’s owner, Sir Thomas Cullinan (The Cullinan Diamond).

            Even though the Cullinan was not a complete crystal, it was a fist-size stone of gem quality.  At the time it was discovered the Premier Mine was the largest of Africa’s diamond pipes.

(fig 1…check link)


The Rough Cullinan Diamond

            The Cullinan was sold to the Transvall Government and presented to King Edward VII for his sixty-sixth birthday (Famous Diamonds).  It was then sent to Amsterdam in 1908 where the Asscher Diamond Company was located.  The Asscher Brothers, were well known diamond cutters.  Several months of studying the stone and planning the cut took place before the event.  The cleaver, Joseph Asscher, would follow the octahedral grain.  He was attended by a doctor, nurse and several professional diamond cutters. The cutter, before performing the cleave, puts a small nick, called a kerf along the direction of cleavage (Encyclopedia of Science and Technology).  The first cleave was unsuccessful; it shattered the thin steel blade that was placed in the kerf.  On the second attempt, the stone split exactly as planned (Rock and Gem).  After the successful cut, Mr. Asscher passed out from the stress generated from cleaving the stone.  It was then cleaved again and again until it was cut into nine major stones and 96 smaller stones (The Altobelli Jewelers).

            Nine major gems were cut from the Cullinan and best known of these is the Great Star of Africa, also known as the Cullinan I.  Designated as the largest polished diamond in the world, it is a 74 faceted pear-shaped stone weighing 530.20 carats and presently encased in the Royal Scepter of the British Crown Jewels.  The Cullinan II is a 317.40 carat cushion cut stone known to be the second largest polished diamond and called the Lesser Star of Africa.  This stone is set in the Imperial State Crown (Diamond Directory). 

The Cullinan II

– aka the Great Star of Africa

 (fig. 3 and fig. 4…check link)


          A pear shaped stone of 94.40 carats, the Cullinan III can be worn with the Cullinan IV which is a 63.60 carat square-cut diamond.  The Cullinan V is a triangular pear-shaped cut of 18.80 carats that was originally set in a brooch for Queen Mary (World Famous Diamonds: The Cullinan Diamonds).  The Cullinan VI is an 11.50 carat marquise cut that was originally presented to Queen Alexandra and is now worn by Elizabeth II as a drop on a diamond and emerald necklace.  The Cullinan VII is also a marquise cut weighing 8.80 carats. The Cullinan VIII is a 6.80 cushion cut stone, while the Cullinan IX is a 4.39 carat pear shape cut.  This stone was mounted in a prong set ring for Queen Mary (Worlds Famous Diamonds: The Cullinan Diamonds).  To this day no other diamond of this magnitude and gemstone quality has been discovered.  The Cullinan Diamond remains in a class by itself.

            This was an informative project for me. The research for my paper yielded only a small quantity of information.  Once into the project, I was captivated by the history and beauty of these magnificent diamonds.  I had never known just how large the original Cullinan Diamond was.  It weighed one and a half pounds and was the size of a fist. Experts figured that it had previously been cleaved, naturally, during its growth because they found a surface that was not fully developed..  The largest of the Cullinan Diamonds, nine in all, are presently part of the British Crown Jewels.  However, there appears to be no further information on the ninety-six smaller stones. 


Works Cited


Cullinan Diamond – Wikipedia, the free encyclopedia. 18 April 2005.

Diamond Encyclopedia of Science and Technology: McGraw Hill. #5

Jones, Bob. Minerals in Depth: Diamonds. Rock and Gem Feb. 1979

The Altobelli Jewelers. 22 March 2005.

The Cullinan Diamond. 5 April 2005.

The World’s Most Famous Diamonds – Cullinan. 18 April 2005.

World’s Most Famous Diamonds. 18 April 2005.

Worlds Famous Diamonds:The Cullinan Diamonds. 5 April 2005.>