Since Argyle Diamond Mine was officially opened in 1985 it has produced over 600 million carats of diamonds. By volume this mine is the largest producing diamond mine in the world but only about 5 percent of the stones produced are considered gem-quality. Other diamond mines usually have about 20 percent considered gem-quality.
There are three primary causes of color variations in diamonds. The first is some type of foreign element was trapped inside the diamond. Nitrogen is the most common element and is responsible for yellow or orange coloration. If boron is responsible then the diamond will be a blue color. The second cause of color variations in diamonds is Natural Radiation and it will cause a green color. These are all considered type I diamonds.
Type II diamonds have very few if any nitrogen impurities in them. They get their coloration due to structural anomalies caused by Plastic Deformation during the crystal growth. The intense pressure changes the lattice structure of diamonds and has led to the formation of red, pink, brown, and champagne colored diamonds.
The Type II diamonds are rare and constitute less than 2 percent of the gem-quality diamonds available. Most of Australians production of diamonds are of the Type II verity and are usually a steely blue or grey due to scattered boron within the crystal matrix.
Argyle Diamond Mine produces over 95 percent of the Champagne colored diamonds and they have developed a color grading scale that is used by the majority of the gemologists today. Champagne diamonds range from light straw color to deep rich cognac color.
Argyle color grading scale for Champagne Diamonds:
C1 - C2 = Light Champagne
C3 - C4 = Medium champagne
C5 - C6 = Dark Champagne
C7 = Fancy Cognac
The Earth Star
First found in the Jagersfontein Mine in May 1967 and the rough gem was 248.9 carats. It was cut into a pear-shaped and weighted 111.59 carats and is considered one of the largest pear shape cognac colored diamonds in the world. It was purchased by Stephen Zbova, of Naples, Florida in 1983 for $900,00.
The Golden Jubilee
This diamond is currently considered as the largest faceted diamond in the whole world. Also known as the fire rose cut diamond, this diamond has a unique fancy yellow-brown color that made it one of the most beautiful pieces of stone ever unearthed.
