Benitoite: Rare California Gemstone

Benitoite is a rare and captivating gemstone known for its intense blue color and exceptional brilliance. Benitoite is a rare blue barium titanium silicate mineral, found in hydrothermally altered serpentinite. Beniotite is a very rare mineral that was discovered in 1907 in San Benito County in California.

It was originally mistaken for sapphire. Benitoite fluoresces under short wave ultraviolet light, appearing bright blue to bluish white in color. The more rarely seen clear to white benitoite crystals fluoresce red under long-wave UV light.

Benitoite occurs in a number of sites, but gemstone quality material has only been found in California. In 1985 benitoite was named as the official state gem of California.

Benitoite has the rarest form of crystal structure in the world. It belongs to the Hexagonal System, it's Class is Ditrigonal -Dipyramidal. It's light dispersion or internal fire is greater than that of diamond. Dispersion is the splitting up of white light into its individual wavelengths, what we see as colors. A benitoite that has good clarity, color and cut will show greater fire than a diamond.

Left Photo By: The Mineral Gallery, Inc. Right photo by: SpiriferMinerals

The blue Benitoite on a white Natrolite matrix and usual association with black Neptunite makes a very aesthetic mineral specimen. Benitoite has a rare 5 pointed crystal form, and an even rarer 6 pointed form, "star of David", with about 24 samples known.

Benitoite is associated with other rare minerals such as black-red neptunite, snow white natrolite and brown-yellow joaquinite. Since the only source of this rare combination occurs at San Benito County, California

With the color of the most valuable tanzanite, it is easy to see why it is so valued. Gem quality Benitoite can be worth more than Diamonds, Sapphire, Ruby, Emerald or Tanzanite. A clean, rare 1 carat cut benitoite sells between  $6500 and $8000, depending on color, cut and clarity.

The cost increases greatly as the size of the cut stone increases due to the rarity of large facet grade crystals. Current market pricing of clean, good color, and well cut faceted benitoite over 2 carats, is $10,000 per carat. Even uncut, rough stones and good mineral samples in matrix can run in the thousands.

It is one of the only gemstones that is naturally deep blue in color, not needing heat or any other treatment to achieve it's color. It can be found in differing shades of blue, violet, white, clear, and on very rare occasions very pale pink, but the Deep Blue color is the most desirable. Science still cannot identify exactly what gives benitoite it's amazing color, and scientists have been unable to duplicate or replicate benitoite's crystal growth or fluorescent nature.

Properties of Benitoite

  • Chemical formula: BaTiSi₃O₉
  • Color is typically blue, but also colorless and yellowish.
  • Luster is vitreous.
  • Transparency: Crystals are transparent to translucent.
  • Crystal System is hexagonal; bar 6 m 2
  • Crystal Habits include the flattened six faced dipyramid that has a distinct triangle shape often modified by minor faces. Also found as small grains.
  • Cleavage is absent.
  • Fracture is irregular.
  • Hardness is 6 - 6.5
  • Specific Gravity is approximately 3.6 (above average)
  • Streak is white.
  • Other Characteristics: Nearly all specimens fluoresce blue under UV light.
  • Associated Minerals include serpentine, neptunite, natrolite, joaquinite, sanbornite, taramellite, albite and fresnoite.
  • Notable Occurrences include only the mines of San Benito County, California, USA for good excellent crystals. SW Texas produces tiny grains in eocene sands as well as some other California localities.
  • Best Field Indicators are crystal habit, fluorescence, color, associations and locality.

Where to Find Benitoite in California

Although commercial mining is no longer being conducted at the mine, People could now dig thru the old mine dumps, tailings and virgin ground to try and find their own treasured jewels. The Fee dig is presently only open on the weekends and will require a phone reservation. All reservations require a phone call for confirmation.

- $70 per person
- Kids 12 and younger, only $20
- Seniors 70 and over with proof of current Rockhound Membership from any Federation Club is half price, $35
Reservations must be made via a phone call: (559)-287-4096
Address: 48242 Los Gatos Creek Rd, Coalinga, CA 93210

See also: 
Types of Iridescent Gemstones & Minerals
How Does a Trapiche Emerald Form?
Types of Mineral Inclusions with Photos
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