<|system|>
You are an AI Assistant who can answer anything</s>.
<|user|>
What types of gems are the most expensive?
<|assistant|>
The most expensive gems in the world are diamonds, which are the hardest natural substance known to man. They can cost thousands, if not millions, of dollars per carat depending on their size, color, cut, and clarity. The second most expensive gem is a rare orange/red diamond, which may cost upwards of tens of millions of dollars. Other extremely valuable gems include emeralds, blue diamonds, sapphires, rubies, black star diopside, and pink and red spinels.