A Bit of Blue Gemstone for a Friday

As I've mentioned a few times, our new Science Community Center at Modesto Junior College is opening soon. Most of the first floor will be devoted to the vastly enlarged Great Valley Museum along with a planetarium and an observatory. One of the aspects of my involvement has been in developing an exhibit of California's state symbols. What today is a few pictures on a wall in the present museum will in a few weeks be a complete display with a full skeleton of a sabertooth cat (our state fossil), a gold specimen (our state mineral), a big chunk of beautifully glossy serpentine (our state rock; yes I know it's called serpentinite, but the legislature was unaware of this) and some of others like our state grass, bird, and flower.

Today I got to take a really close look at our state gemstone, which is one of the most obscure such designations in the United States! Can you say what this beautiful blue mineral is called?

The first Europeans to discover it thought it was sapphire. It's so rare that it was only described for the first time in 1907. And gem-quality specimens are found in abundance at only one mine in the entire world. It is a barium titanium silicate mineral called benitoite (after San Benito County, where it was found).

Benitoite crystallizes in the hexagonal crystal class, but forms a rare triangular type of crystal within the class. It is a beautiful blue color, but is a bit on the soft side (6-6.5) for extensive use in jewelry. It is also known for fluorescing in ultraviolet light. The matrix in which it is found is called natrolite, and sometimes elongated crystals of neptunite are associated with the benitoite.

It's a beautiful specimen that we'll have on display. Don't miss it if you are ever in Modesto!