Cochise College           Student Papers in Geology

Geology Home Page                   physical geology  historical geology  planetary  gems           

Roger Weller, geology instructor

wellerr@cochise.edu

diamonds
by Juan Parra
Physical Geology
Spring 2010
                  

  

                                                                    Diamonds
 
 
          Diamonds are made out of carbon. Their worth depends on shape, hardness and transparency. They are the hardest gems. The chemical bonds that hold the diamonds together are less strong than pure carbon graphite. In graphite the atoms can slide over one another.



          Diamonds can cut all material that exists. They can not be scratched and they resist anything.

          One is the softest diamond as ten is the hardest in the Mohs scale of mineral hardness. The hardness depends on purity. The hardest diamonds can only be scratched by other diamonds. Even though it maintains polish well.

          The hardest diamonds came from Copeton and Bingara fields. They are located in New England and New South Wales. They are small and are used to polish other diamonds.

           The color of diamonds depends on lattice defect and impurity.

            Pure diamonds show light and are clear crystals. Nitrogen is the biggest impurity in diamonds. This makes the color yellowish and brown. Boron makes them gray blue color on them. Irradiation makes them green. Plastic deformation causes brown, pink, and red diamonds. Colored diamonds are defections that cause them to be like this.
 

brown diamonds



blue diamonds



pink diamonds





           In 2008 the wittlebach diamond which was the color blue and belonged to the king of Spain cost 24 million dollars at an auction. In 2009 a blue diamond was worth 9.5 million dollars. However that same year a pink diamond costed 10.8 million dollars in Hong Kong.

           Diamonds can be formed in meteorites impact craters. They are called nano diamonds. However not all diamonds originated on earth. They can be deposited by an asteroid impact. About 3 billion years ago. They may have been made in supernovas. They can also be formed in the depth of a volcano. But this is rare.

           Diamonds are made in the process of cutting. They can be split because they are brittle . This is done with skills, scientific knowledge, tools and experience. This is to make it a jewel with certain angles to show luster and weight.

                                                       Production
 
              About 130 million carats of diamonds are found within a year. The value of these is about 9 billion dollars. Most diamonds come from Africa and some came from Canada, India, Russia, Brazil and Australia. These are mined from volcanic pipes. Diamond crystals near and come from the depths of the earth. This happens because of high pressure and temperatures that brings them to the surface of the earth. Blood diamonds or conflict diamonds are distributed by African paramilitary groups. The chain of diamonds is controlled by powerful businesses which are located in small numbers around the world.          
 

          Solid diamond ore has small diamonds.  The ore is smashed with care so large diamonds are not lost.  They can then be sorted by density.  The density of a diamond is located with x-ray fluorescence.  The final sorting is by hand.  Before the x-ray was introduced people would use grease belts.  The diamonds have the inclination of sticking to grease more than other minerals in the ore.

          In the past diamonds ere only found in alluvial deposits in southern India.  India was the leading world production center since the discovery of diamonds in the 9th century B.C. through the 18th century A.D.  But by the late 18th century the commercial potential was running low.  At that time the commercial potential in India was vanishing.  The business by Brazil as the first Non-Indian diamonds were found in 1725 A.D.

          In the 1870's diamond fields were discovered in South Africa.  A total of 4.5 billion carats have been found since then.  However in the last 10 years nine new mines have produced these diamonds.  There is also four more to be open soon.  A couple are in Canada, Zimbabwe, Angola, and in Russia.  Some diamonds are synthetic and are made in a laboratory.  Unlike natural diamonds that come from the Earth.  Rough stones are in large demand.  That is why synthetic diamonds are made.  They have been processed for about half a century.  Now it has been possible to create diamonds in larger sizes.  Commercial diamonds are usually yellow and they are made in high pressure temperatures.  This yellow color happens by impurities of nitrogen.  There is also blue, green, and pink because of baron after synthesis.

          Chemical vapor is another way of making diamonds.  This growing process happens in low pressure (below atmospheric pressure).  This happens when gasses are mixed.  Mostly 99% methane to hydrogen, it goes in a chamber, and splitting them to chemically active radicals in plasma turned on by microwaves, hot filament, arc discharge, welding torch, or laser.  This is used for coatings and it can produce smaller crystals.

          Natural diamonds are about 170 million carats.  A buyer could buy a synthetic diamond because they might be looking for a certain color diamond because only .01% are colored.



          Cubic zirconium has a similarity to diamonds but is lower in price and that brings more customers.  Zirconium and moissanite are synthetic.  So the buyer has to be aware of what he is purchasing.

          The diamonds beauty and rarity has led to its value through out mankind's history.


 

Photos are from Roger Weller