Benitoite

Mineral(s): Benitoite on Natrolite
Locality: California State Gem Mine (Dallas Gem Mine), New Idria District, San Benito Co., California, USA

This is California's state gemstone, benitoite. Although technically this mineral can be found in other parts of the world, the only locality of any real significance is in central California. It is a highly coveted gem, with gemstone prices going for often more than $4000 per carat, which is a lot more than a diamond of standard quality. The value of this mineral with further increase now that the only working mine has closed due to the entire area being deemed unsafe due to asbestos hazards (as assertion by the California government that is entirely untrue, given that the type of asbestos in the region is mostly harmless serpentine - not that any government official would bother to differentiate).

Here is a 1 cm triangular blue crystal of benitoite (along with other incomplete crystals) on a matrix of massive white natrolite, a mineral that is ubiquitously found in association with it. If you happen to have a short wave UV light, both minerals can fluoresce as well.