Blog-Gems5a While beauty is in the eye of the beholder, value is tied directly to rarity. With more than 4,000 mineral assemblages on earth, these gemstones are the most expensive in the world. Diamond - $15,000 per carat The most well known of the gemstones, the diamond is the centerpiece of most engagement rings. Diamonds are pure carbon and are created by the combination of high pressure and temperature. The stones are arranged in a diamond lattice which accounts for its incredible strength and durability. Serendibite - $18,000 per caratBlog-Gems4a An extremely rare gemstone and mineral originally discovered in Sri Lanka in 1902, serendibite has a complex chemical formula with many side branches that include calcium, boron, aluminum and more.   Grandidierite - $20,000 per carat Blog_Gems3aThis very rare gem can fetch up to $20,000 per carat and was first discovered in Madagascar in 1902. It is commonly found as an accessory mineral and features a semi transparent, sea-glass like hue and was named in honor of French explorer Alfred Grandidier. Taaffeite - $35,000 per carat Blog_Gems-2aOften misidentified as spinel, this gemstone was first discovered already cut and polished in Dublin, Ireland in 1945. At the time, the gemstone was mislabeled but was determined to be a new, unidentified gem. Taaffeite is primarily found in Sri Lanka and Tanzania. Red Diamond - $1,000,000 per carat Blog_Gems-1aThe most expensive gemstone is the red diamond. With less than 30 red diamonds accounted for around the world, most being less than half a carat, they are exceedingly rare. The red color does not come from impurity, but instead it's derived from plastic deformation of the crystal lattice. The famous 5.11 ct. Moussaieff Red Diamond was acquired in 2011 for $8 million and is the largest red diamond discovered in the world. Click here for a complete list of the most expensive gemstones.