California Gemstone or Gem

Benitoite

BaTiSi3O9 - Barium Titanium Silicate

Adopted in 1985
 

Benitoite, BaTiSi3O9 - Barium Titanium Silicate,  was designated as the official State Gemstone in 1985. Sometimes called the " blue diamond", it was first discovered near the headwaters of the San Benito River from which it derived its name. The gem is extremely rare and ranges in color from a light transparent blue to dark, vivid sapphire blue, and occasionally it is found in a violet shade.

Benitoite is a somewhat obscure, but wonderful gemstone mineral that was only discovered at the beginning of this century. Benitoite was discovered in 1906 near the headwaters of the San Benito River, in San Benito County, California. It has a sapphire blue color and was first thought to be a variety of sapphire.

Benitoite is found with other rare minerals such as black-red neptunite, snow white natrolite and brown-yellow joaquinite. A rare cluster of blue benitoite and black neptunite on top of a crust of white natrolite is a treat for mineral collectors.

Benitoite occurs in serpentine, California's state rock. The mineral benitoite is the only natural occurrence of the ditrigonal-dipyramidal class, hexagonal system.

It is the only gem known in its crystal class. Its beautiful triangular crystals were predicted mathematically before any material in that class was ever found. The cut stones are brilliant blue, from colorless to deep blue and full of fire, since dispersion is only slightly less, equal to, or slightly higher than diamond. In recent years a few pink stones have been faceted. Hardness is satisfactory at 6.5, but it requires some care in setting and wearing it. Stone sizes are small, as only tips of crystals are gemmy. Gems much over one carat are uncommon and only about five a year are over two carats.

The sapphire-blue or colorless crystals are small; gem quality specimens larger than two carats are rare.Faceted stones are usually under 1 carat; the largest documented stone is 7.8 carats and resides at the Smithsonian. Benitoites sell for over $1000 per carat and the price has been raising rapidly as the deposit has been largely worked out and available gems sold.

One of the finest and rarest of gemstones, benitoite combines the color of fine blue sapphire with the dispersion of diamond.