Among fancy colored diamonds red diamonds have special place, not only because these these diamonds are among most desirable diamonds, but also because they are extremely rare, so rare that many jewelers have never seen one of this really unique diamonds. Out of all colored diamonds red diamonds are the rarest of them all.
When saying extremely rare that doesn't only apply to natural red diamonds as it is also very difficult to find even enhanced red diamonds, so you can imagine how precious red diamonds really are. So even if you have plenty of money finding natural red diamond will be more than difficult.
Natural red diamonds are mostly found at Argyle mine in Australia, though in very limited number which has tremendous impact on their price which is in most cases astronomical. The biggest red diamond ever found is known under the name of "Red Shield" and has only 5,11 carats which is more than hundred times less than largest diamonds of any kind. Another famous red diamond was "Hancock Red" that for its weight of 0,95 carats was sold for incredible price of $880,000 at Christie's New York in April, 1987.
Red diamonds are really elite among fancy colored diamonds, and only few lucky (and extremely wealthy) people have luck to buy these unique diamonds. Many other are forced to look for alternatives in different color, or rubies which are much more affordable.