|Benitoite in a matrix of neptunite from San Benito County, California.|
Photo by Rob Lavinsky
Benitoite is a one-of-a-kind gem since it is only found in one place in
it is also the state gemstone of California
as of 1985. The stone itself is a rare
variety of barium-titanium silicate found in hydrothermally
altered serpentine. Benitoite reacts under shortwave ultraviolet light
fluorescing light blue in color. California
As a mineral benitoite was described in 1907 by George D. Louderback who named it benitoite because it was found near the headwaters of the San Benito River of San Benito County,
The stone was one of the first if not the first mineral to be studied under
x-ray diffraction. California
|A single crystal of benitoite in matrix.|
Photo by Lech Darski
This stone is usually found an unusual set of minerals including the minerals that make up its host rock. The associated minerals usually include naturolite, neptunite, joaquinite, serpentine and albite. Benitoite is very rare mineral that is only found that it few locations among them are places in
It is also been found in San Benito County, California
and Arkansas . It
is usually found in glaucophane
schist as inclusions in veins of naturolite. Benitoite mining is allowed for a fee in the
benitoite mine in the Japan
management area in central Clearwater .
Collecting is by appointment only! California
This gemstone is typically colored various shades of blue although it can also appear as colorless or even have a yellowish caste. Its crystals can vary from transparent to translucent with visible inclusions with a vitreous luster.
|A single crystal of benitoite with no matrix.|
Photo by Rob Lavinsky
When found its crystals are hexagonal; bar 6 m 2 that in crystal habits include six place dipyramid flattened shapes having a distinct triangle shape that is often modified by having minor faces. At times it is also found as small grains.
Benitoite has no cleavage and its fracture is irregular. Other distinguishing features are its hardness ranging from 6 to 6.5 on the Moh’s scale of hardness. Its specific gravity is 3.6 making it denser then most other minerals making it capable of being separated by gravity methods such as panning. The mineral also displays a white streak.
|A faceted example of benitoite|
Photo by Fastily
This mineral is counted among those that fluoresce under the influence of ultraviolet light displaying a blue light. Minerals that are associated with benitoite include serpentine, neptunite, natrolite, joaquinite, sanbornite, taramellite, albite and fresonite.
Benitoite gems are only found in three mines located in
good to excellent crystals are found. The
only other occurrences are in Eocene aged sands in southwestern San
Benito County, California
along with another few localities in Texas . These occurrences are only small grains found
in sand. California
|Benitoite under ultraviolet light.|
Photo by Parent Gery
If you are searching for this mineral the best field indicators its crystal habit, the fact that it displays fluorescence in blue, its distinctive color, the minerals it is associated with and the locality. The fact it is associated with bodies of serpentine suggests that it might be found in localities that have been identified as suture zones where geologists feel that serpentine is metamorphosed oceanic crust that has been caught up in earth movements associated with the collision of two continental plates,