Top 10 Most Expensive Gemstones

"I adore wearing gems, but not because they are mine. You can't possess radiance, you can only admire it."
Elizabeth Taylor

This is an objective list based on info from Forbes.
The Top Ten
1 Red Diamond - $1,000,000 per carat

Red is the rarest diamond color in the world.

2 Taaffeite - $35,000 per carat
3 Grandidierite - $20,000 per carat
4 Serendibite - $18,000 per carat
5 Diamond - $15,000 per carat

The colorless variety

6 Alexandrite - $12,000 per carat

Alexandrite changes its color (alexandrite effect) dependent upon the nature of ambient lighting. Alexandrite may even display a big color change, such as from greenish to reddish, with a change in source illumination.

7 Red Beryl - $10,000 per carat

Red Beryl is mined in Thomas Range, Utah (Wah Wah Mountains), which is the ONLY location where gem-quality crystals can be found.
Like diamonds, pure beryls are by nature colorless and red beryls are really rare - there is one gem-quality red beryl crystal for every 150,000 gem-quality diamonds.
Red Beryl is also found in New Mexico and Mexico but most stones are too small and deemed unworthy of faceting.

8 Musgravite - $6,000 per carat
9 Benitoite - $4,000 per carat
10 Poudretteite - $3,000 per carat