What is the rarest element?

Could you please explain to me what is considered the rarest element on Earth? Is it a naturally occurring element that is incredibly difficult to find, or is it a synthetic one that has been created in a lab? How does its rarity impact its value, both scientifically and economically? Are there any specific industries that rely heavily on this rare element, and if so, how does its scarcity affect those industries? I'm intrigued to learn more about this fascinating topic.