Benitoite is one of the rarest gemstones that is relatively new. It’s a blue barium titanium silicate mineral that fluoresces under UV light. It was first discovered in 1907. Also, it is an exquisite and most valuable gemstone. Due to its rarity, it can be extremely expensive. In addition, Benitoite rarely exceeds 2 carats.
The biggest Benitoite source is the Diablo Range, in San Benito County, California. Hence why in 1985 Benitoite was named as the official state gem of California.