Rare California Minerals: Benitoite Jewels from the United States
The Benitoite Gem Mine, nestled in the San Benito County of California, remains the only known source of facet-grade benitoite gemstones worldwide. Discovered in 1907 and designated as California's state gem in 1985, this unique mine has a rich history and ongoing mineral collecting interest.
Despite conflicting reports, large-scale commercial mining appears to have ceased around 2005, though small-scale or recreational mining and specimen sales continue. The mine and surrounding area are still active, with vendors offering benitoite from the California State Gem Mine and hands-on digging experiences available for visitors.
Benitoite is a rare blue gemstone that forms in the hydrothermally altered zones of the blueschist, specifically where amphibole and pyroxene show recrystallisation. It was initially mistaken for blue diamonds, blue obsidian, and spinel before being identified as a new mineral. The unique geology of the New Idria region, with its serpentinite body and captured rocks from the Franciscan Complex, played a crucial role in the formation of benitoite.
Crystals are typically smaller than one centimeter, with many being highly included. Cut stones are typically smaller than one carat, but larger stones, such as the 15.42ct largest cut benitoite, have been produced over the years. The common form that benitoite crystalises in is a ditrigonal-dipyramidal habit, a very rare form in trigonal crystals.
Benitoite can come in a beautiful range of colors from blue to slightly purplish-blue, or white to colorless, with very few stones being naturally pink. Most stones are not treated in any way, but an orange color can be caused in some stones through heat treatment.
The Benitoite Gem Mine operated from 1907 to 2005 and was reclaimed in 2005, now open as a small pay-to-dig operation. Out of less than 10 known locations worldwide, only three are outside of California (Japan, Australia, and Arkansas, USA).
The name 'benitoite' was officially given to the mineral on July 30, 1907, by Associate Professor of Geology at the University of California, Berkeley, Davis Louderback. The mine's ongoing availability for collectors and tourists ensures that the historical significance of the Benitoite Gem Mine continues to be preserved.
- Researchers in the field of gemmology frequently study the unique properties of benitoite, a rare blue gemstone, to better understand its formation and characteristics.
- Many diploma programs in gemmology and related fields offer courses on the identification, cutting, and evaluation of rare gemstones like benitoite, providing students with valuable skills and knowledge.
- The lifestyles of fashion-and-beauty enthusiasts and jewelry collectors often include the pursuit of unique and exotic gems like benitoite, which can add a touch of luxury to their wardrobe or collection.
- Home-and-garden design aficionados might incorporate benitoite stones into their decor, using them in everything from kitchen countertops to small decorative accents, reflecting their appreciation for the precious stone's beauty.
- Travelers planning a trip to California might include a visit to the Benitoite Gem Mine, a unique tourist destination that offers hands-on digging experiences and the opportunity to purchase the state's official gemstone.
- Sports enthusiasts and outdoor adventurers might be drawn to the exciting experience of small-scale mining for benitoite at the mine, turning a hobby of mineral collecting into a fun and engaging activity.
