The collision and crustal compression would require millions of years to complete. ![]() Instead, the rock masses collided at a velocity of a few centimeters per year. This plate tectonics collision was not a sudden deformation like the impact of two automobiles. These forces are thought to be responsible for dislocating carbon atoms in many of Argyle's diamonds. About 1.8 billion years ago, an ancient continental collision compressed the rocks. The Argyle mine is located in an area of Australia that was subjected to the compressive forces of the Proterozoic Halls Creek Orogen. At present, no new sources of even occasional red diamonds are known. ![]() The diamond market may have an even more limited number of new red stones entering the market, because the Argyle Mine is expected to close in 2020. These produce diamonds that are brownish red, purplish red, and orangy red. Modifying colors include brown, purple, and orange. Slightly less rare are diamonds with a modified red color. In the 30-year period between 19, Argyle produced fewer than 20 carats of Fancy red diamonds - and that was from the world's leading source of red diamonds. The Argyle Mine, the leading producer of red diamonds, came online in December of 1985, and that is when a few red diamonds per year started appearing at the GIA laboratory. ![]() The GIA lab grades more diamonds than any other lab in the world, and the fact that no pure reds were submitted for grading over a 30-year period is a strong testament to their rarity. Red diamonds are so rare that between 19, no diamonds with a pure red color were graded by the Gemological Institute of America.
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