Benitoite is a barium titanium silicate. It was first discovered in 1906 near the San Benito River in California. A mineral prospector was searching for mercury and copper near the river when he found small blue crystals he assumed were sapphires. He then sent the stones to G.D. Louderback at the University of California. Louderback immediately recognized the stones as new, unknown minerals, and named them benitoite after the river where they were found. In October of 1985, benitoite was selected as the official gemstone of California. In fact, California is the sole place benitoite is found and as such, it is very rare, and therefore popular amongst gem collectors.
Benitoite's popularity is also a result of the crystals' high brilliance - its 
diamond-like fire, and its beautiful natural blue color. Production of benitoite has recently stopped, as the mine in which the crystals were found has been exhausted. It is therefore becoming even more difficult to find. You will definitely not be able to find this crystal at your local jewelry store. Cut stones of benitoite up to .25 ct are available, but stones over one carat are extremely rare. In fact, the largest crystal ever found was only nine carats.
Benitoite ranges in color from colorless to pink, to many different shades of blue. Blue is by far its most common color. The most highly coveted color of benitoite is a magnificent 
sapphire blue. These beautiful stones are actually sometimes mistaken for sapphire. However, benitoite has a marked blue and colorless dichroism which sapphire does not. The stone can appear blue or colorless when viewed from different angles. The most beautiful blue color is seen when looking through the side of the crystals, rather than from top to bottom. When untreated, the blue color of benitoite is natural, and the stone has a stable reaction to light.
Because benitoite can display two colors, it must be cut in a very specific way, in order for the blue to show more than the colorless parts. Benitoite crystals are shaped like flattened triangles, have a hardness of 6.5, and a vitreous luster. Benitoite's strong dispersion is exceptional, and is similar to that of diamonds. However, benitoite's dispersion is not as obvious as diamond's, as its blue color masks this trait. Benitoite should be cleaned in warm, soapy water. Do not use ultrasonic cleansers on the stone and avoid any acids or rapid temperature changes.
