Red diamond is the rarest and the most expensive gemstone in the world. There is only one deposit producing red diamonds, and it is located in Australia. Moreover, there are very few red and nearly red diamonds even there. Just a couple of carats can be produced per year. The gems weighing more than 0.1 carats are sold only at the world class auctions. They cost a sight of money.
Here is a red diamond from the Argyle mine (Australia) in the Aaron Basha ring. It is worth millions of dollars. The ring is made of pink gold and features a large diamond of a fancy red color weighing 0.59 carat.
The Red Fire collection of the Leviev jewelry house (above) includes a magnificent ring with a red diamond framed with white ones. The collection is priced at about $15 million.
At the 2011 jewelry auction in Hong Kong there was a diamond ring with a red diamond weighing 1.92 carats. Unfortunately, there is no information whether this lot was sold and what the price was.