State Gemstone for California

State Gemstones are interesting, some are more obvious than others, some are more rare than others. The State gemstone for California is no exception, and is no longer mined commercially.


The State Gemstone for California is actually Benitoite, when this stone was first discovered in 1907 it was originally thought to be Sapphire, looking at the color you can understand why, but after more thorough testing the dispersion and birefringence values proved otherwise.

This gemstone can range in color from a light transparent blue to Sapphire Blue, and occasionally a more blue/violet this color almost reminds me of a shade of Tanzanite.

Benitoite is now considered to be a rare gem and the mine in San Benito county has been closed since 2005. This mine was considered to have found the best quality gemstone.

Most of the gems you find mined in more recent years will be smaller stones unless you are lucky enough to discover something in an estate collection which will then likely be very expensive.

Although not as tough as a diamond it can still be a good choice for everyday wear in a ring, but you will not find it in jewelry stores, most pieces will be found for sale by individual artisans or as stated previously in estate pieces.

There is still one mine open in California to visitors, so you may be able to go and mine your own but for a fairly large fee.

I would love just a little gemstone for myself but its rarity is also reflected in the price, Forbes list Bentoite as one of the 12 most expensive gemstones in the world at $4000 per carat   ( with the deep medium blue being most expensive and white costing the least although still around $1600 carat.

Although rare, gem quality Benitoite is still used in industry to align electron microprobe beams. It is not that hard of a gemstone, on the Moh’s scale it is 6-6.5, to give you an idea quartz rates as a 7.

A new “Gems and Minerals” exhibition is coming to San Diego Natural History Museum later this year. Take a look here for more details – Gems and Minerals Exhibition opens November 2018 in San Diego.  There are sure to be some beautiful examples on display there.

Some other gems that have been mined in San Diego County include Watermelon Tourmaline, Quartz and Topaz.

“Gems seduce us with their sparkle. But did you know that every glittering ruby, sapphire, diamond, and opal has a history as old as the Earth itself? A gem isn’t just a pretty bauble—it’s a rare and wonderful by-product of the tremendous forces that have shaped our planet. Discover how the same Earth processes that build landscapes produce dazzling gemstones and precious metals—even right here in San Diego County, one of the most famous gem-producing regions in the world. The exhibition features a stunning selection of spectacular natural mineral crystals, exquisite jewelry, and works of art.”

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