Question: what are most expensive gemstones?
Answer: Tanzanite. $1,200 per carat. ... 
Black Opal—$9,500 per carat. Dark and mysterious, the black opal is very different to its lighter, white and fiery sibling. ... 
Red Beryl. $10,000 per carat. ... 
Musgravite. $35,000 per carat. ... 
Alexandrite. $70,000 per carat. ... 
Emerald. ... 
Ruby—$1.18 million per carat. ... 
Pink Diamond—$1.19 million per carat.