Rare
Means not common, not frequently found. A rare thing is Something that is not seen, found, or happening often; something uncommon or unusual.

Examples:
1- King Charles III bestowed a royal title on a rare golden goat breed. The title Royal Golden Guernsey Goat will apply to the livestock breed anywhere in the world.  
2- The rare painting, which was thought to be lost for centuries, was auctioned for millions of dollars to an art collector.